Wikipedia says: "

Porphyrias are a group of inherited or acquired disorders of certain enzymes in the heme biosynthetic pathway (also called porphyrin pathway). They are broadly classified as acute (hepatic) porphyrias and cutaneous (erythropoietic) porphyrias, based on the site of the overproduction and accumulation of the porphyrins (or their chemical precursors). They manifest with either neurological complications or with skin problems (or occasionally both). An induced clinically and histologically identical condition is called pseudoporphyria. Pseudoporphyria is characterized by normal serum and urine porphyrin levels.

The term derives from the Greek ???????, porphyra, meaning "purple pigment". The name is likely to have been a reference to the purple discolouration of feces and urine in patients during an attack

Here's a quick summary:

Martin has been finding life in Portwenn frustrating since Louisa has left town following their non wedding. Martin considers taking his life in a new direction whilst he runs into ex girlfriend, Edith, who is now a high flying doctor. When Louisa returns to town pregnant, Martin finds his plans in doubt again.

Cornwall, a land of fairytales and natural beauty, continues to offer the best to holidaymakers. For centuries, Britains and travellers alike have journeyed to Cornwall’s pristine coastline and verdant hills in search of a peace not found in modern city life. Whether in search of sun and sport or a simple country escape, nothing opens the door to the hidden delights of this ancient region like the timeless cottages in Cornwall.

For history buffs and lovers of architecture, the whitewashed stone and time-faded slate of the older shops and cottages will send you to daydreaming of times gone by. For the modernists, timber-constructed updated cottages make the most of hillside views and sparkling sunsets.

Cornwall, itself, is a land rich in history and wonder. Often cited as the true land where Camelot once stood, archaeologists and historians have ongoing digs throughout the region and often invite the public in for viewings of discovered relics and exciting re-enactments of jousts and medieval celebrations.

Lying in the southernmost tip of England, Cornwall offers a climate unparalleled in the United Kingdom. If sun and sea are what you’re looking for, Cornwall boasts hundreds of public and private beaches well known for sports and fun such as sailing and surfing.

Perhaps the most prized offerings Cornwall has are its ancient villages, the winding streets walked upon for centuries, the cobbled beauty of buildings that have stood the test of time and ruins of those which haven’t. To have all the Cornish attractions on your doorstep, even if only for a weeklong cottage holiday, is a break from life that we all deserve.

If the daily routine and workload of everyday life is beginning to sharpen your edges, a journey back in time, a stay in a hilltop escape, a visit to a coastline steeped in history and laced in nature, is sure to smooth you out to rights, once more.

Coastline, Cuisine, and Culture
A mini-break or full holiday in Cornwall can save on time, keeping you close to home, but what fun is there to be found in this seaside county? Cornwall has something for everyone.

Port Isaac is an angler’s delight and offers a variety of beaches where a fisherman can try his luck. If you prefer to join the fish rather than catching them, be sure to check out local surfing, sailing, and kayaking.

If food is your flavour, a number of restaurants from casual to cuisine dot the shoreline and winding streets of Port Isaac. From quaint pubs to fine, stone-fronted inns, you can sample the rustic, hardy fare for which the Cornish are known, as well as delicacies using locally caught seafood and regional produce.

Sparing the Change
The sure fire wet blanket on any holiday dream is that big, bold bottom line. Tough economic times leave little hope for the ever-rising costs of airfare, hotels, restaurants, and attractions. One of the greatest benefits of going off the beaten path is avoiding the tourist traps that can so quickly drain your reserves.

Self-catered cottages in Port Isaac offer a great fix for this frustrating problem. Weekly rental prices being significantly lower than those of chain hotels, and the flexibility to prepare your own meals, as needed, means less money out-of-pocket and more fun to go around.

Holidays are often the first luxury to suffer the leaner times, but self-catered holidays in quaint Cornwall cottages offer breaks at a discount over foreign destinations and high-priced hotels.

A typical family of four could quickly find themselves £1000 out of pocket for a week’s stay in an average hotel. Add to this the cost of airfare and ever-rising tariffs on baggage and in-flight meals, plus hundreds in restaurant dining, and a simple week’s break can drastically drain the budget. So, what makes a stay in the self-catered cottages of Cornwall a better option?

Travel: Airline travel is increasingly difficult. When planning a family trip, the prospect of lofty fees and long lines can easily start the holidays on a bad foot. Vacationing closer to home offers many alternatives to air travel. Try a picturesque journey across the U.K. by train. Average return-fare tickets for two adults and two children (London to Cornwall) run well below £200.

Dining: In a self-catered cottage, your dining options abound. A family is not compelled to source out expensive, touristy restaurants for every morning’s breakfast or afternoon tea. With access to a private kitchen, self-catering allows one to partake of the choicest local produce and test one’s own skill at cooking while saving hundreds on costly cuisine.
Entertainment: All the money saved on lodging, travel, and food leaves the budget wide open to explore all the fun and beauty Cornwall has on offer. The Cornish countryside is home to museums, adventure parks, historical tours, and over 150 pristine beaches—all that any family could want lies right outside the cottage door.

Spare the wallet but don’t spoil the fun. Explore the value of a self-catered holiday in the Cornish countryside and see what awaits you in this peaceful family escape.

Wake to a crisp morning in the peaceful solitude of your cottage boudoir and wander the winding streets of this 14th Century fishing village, hand in hand. Pack a picnic lunch and enjoy a quiet niche along Port Isaac’s soothing surf. Rejuvenation and reconnection are the catch of the day in this quaint, historical town.

Port Isaac, while small, offers age old beauty in both manmade and natural forms with whitewashed stone shops, narrow passageways and alleys just waiting to be explored. Make your way to the top of a verdant hill and drink in the timeless vista of hedgerow-lined fields and the blue-grey pool of the peaceful harbour below.

In this little hamlet, romance can lead to adventure. Would coastal kayaking, open sea fishing charters, or medieval jousting festivals light your fire? Port Isaac and the neighbouring regions have all of these, and more. Feel like King Arthur and his Guinevere as you conquer every challenge the Cornish coast can dish out.

Though self-catering allows you the option of quiet home cooked dinners, Port Isaac’s Fore Street and Harbour Front also boast the finest in flavours from casual pub fare to genuine cuisine. Choose from country-style crab dinners, served up with a pint of Cornish Ale at a Victorian Inn, Thai-inspired bistro dishes with ambience to spare, and Cornwall’s finest cookery created from the day’s freshest catch.

When it’s time to escape the noise and travails of everyday city life, step across the threshold of your own romantic hideaway and find the spark inside.

Fishing:

Known for fresh, delicious seafood, fishing abounds near this quaint seaside town. Pick a sunny spot and learn to bait your own hook or charter a seafaring tour for hours of expert tips and a tasty catch to take back to your holiday home. Whether you’re a novice or an expert angler, you will relish the bounty Port Isaac’s fishing waters have to offer.

Adventure:

Only a short drive from your cottage door you can find a variety of action and adventure with paintball, kayaking, cave swimming, cliff jumping and more! For the action-packed vacation, Port Isaac and surrounds provide it all. Suit up and get set for excitement and fun!

Royal Treatment:

Explore the history and legend of King Arthur’s final battle with Mordred and learn why many believe the Cornish countryside may have been home to the fabled kingdom of Camelot. Children will love the magic and wonder of re-enacted jousts, sword fighting, storytelling and music. Adults will enjoy the history and speculation as archaeologists uncover more of the mystery with each passing year.

Beaches:

Don your togs and go for a family romp on the pristine beaches of Port Isaac and the Port Gaverne cove. A centuries-old fishing village, Port Isaac offers historic coastline and award winning natural beauty. Free from the noise and crowding of tourist beaches, you can truly savour the family fun to be had with waterside picnics and a dip in salty waters.

"We have had the golden egg from the filming and we have had enough visitors now," said one resident, Ted Charles. "Surely they have enough footage of Port Isaac on file so they don't need to come back?"

The village is used as a location for the fictional town of 'Portwenn' in the ITV series, which stars Martin Clunes as a grumpy GP.

On Monday night more than 30 residents filled the village school hall to protest to St Endellion parish council about the parking problems.

They said tourists have been dumping their vehicles by a children's play area, and are concerned a child could be killed.

Debbie Pattenden, a mother, said: "We need to take this seriously before we lose one of our children. It is extremely dangerous, especially when they want to go to the park."

Mr Charles added: "We have heard that next year they will be filming from May to August. That would be a complete disaster and the parking problem will only escalate.

"Friends who have enjoyed coming to the village for years have not been able to stay in holiday cottages because they have been rented to the crew."

A B & B owner, Marion Andrews, said the village had become too busy for regular customers who wanted peace and quiet.

In response the parish council said it was writing to the county highways department to request yellow lines to try and ease the parking problem.

David Phelps, chairman of St Endellion Parish Council said parking had been a problem for years but was being exacerbated by Doc Martin fans.

Port Isaac has previously been used for films and other television shows including the 1970s series 'Poldark'.

In recent years, the village has become home, for part of the year, to a number of celebrities, including the designer Laurence Llewelyn-Bowen, the actress Julie Peasgood and the presenter Lorne Spicer.

Nearly 40 per cent of properties in the village are now second homes and the cost of the average home has been pushed to £280,000.

A spokesman for ITV said she was unable to comment on the complaints as a series of Doc Martin had not been filmed this year.

She said: "We have not been near Port Isaac since 2007 and have no plans to return until 2009."

Doc Martin has attracted up to 10 million viewers in Britain and is a hit in more than a dozen countries including Australia, Belgium and Romania.

Local estate agents Estuary Estates said the show had raised the profile of the village and was seen as an added attraction.

A spokesman said: "They are making a fourth series of Doc Martin, so we always mention this in the particulars. It is a very sought after area."

Speaking previously, Clunes said: "I love working on Doc Martin, being in Cornwall, and being able to work with my wife Philippa, who is the producer.

"At the end of the day's filming we were able to go back to a beautiful house along the coast from Port Isaac, which has stunning sea views.

"And it means I was home before my daughter Emily had to go to bed, which doesn't happen when I am filming in London."

The exterior of the doctor's surgery is a detached cottage up a steep hill overlooking the harbour, and with stunning views out to sea.

The Golden Lion, the only actual pub in the village, became the Crab and Lobster in Doc Martin. The interior of the 18th century building was taken over by cast and crew for several days during the shoot. The Old Drug Store, which is now a gift shop, was transformed into the local pharmacy. Ours, the coffee shop in the centre of the village, stayed open all night to keep the cast and crew supplied with cappuccinos and hot chocolates during night shoots. And the Cornish pastie shop next door did a roaring trade during the day.

The village hall was the setting for the Portwenn dance, and a farm just outside Port Isaac became Aunt Joan's smallholding. A barn on the outskirts of the village was converted into a studio for some of the interior scenes.

Port Isaac is the one of the most remote villages in the UK- the nearest town, Wadebridge, is ten miles away. In 1820 it was described as "secluded from the rest of the world". Access to the village is via narrow winding roads, which will only allow one vehicle at a time. So much of the movement between locations was done on foot.