The seabed off the Cornish coast seems to have almost recovered after an oil tanker spill in 1967, writes Paul Rose, expert diver and presenter on BBC programme Britain's Secret Seas.

The Torrey Canyon is the largest shipwreck in British waters, and as she sits a long way from shore amongst the same hazardous rocks that she ran on to, its not the easiest wreck to get to.

On Saturday, 18 March 1967, she ran aground carrying over 119,000 tonnes of crude oil, which gushed out into the pristine Atlantic waters.

She had run into one of the infamous Seven Stones rock pinnacles, which lay 15 nautical miles west from Lands End and seven nautical miles from the Scilly Isles, which make it a hard wreck to reach.

We believe our team is the first to film the wreck, which is in an area often hit by storms. As I rolled off the boat into heaving waters caused by constant huge Atlantic swells, I entered a great swaying underwater forest of kelp.

The water was gin clear and the huge kelp fronds were in a mad rhythm of bending, then standing straight up, swinging and heaving to the forces of the sea.

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It was a great, vibrant start to the dive, but it looked to me as if we had missed the Torrey Canyon completely, as after all she is said to be well broken up over 2 sq km of the seabed.

I then realised that I was on the wreck - the huge hull plates have so much life on them that they look just like rocks or the bottom. The sea has reclaimed the wreck and it is teeming with life.

Things started to make sense and as I swam along the steel plates I joined large schools of wrasse, pollock and pouting. Some of the schools were moving purposefully along the wreck sides and others had relaxed into shoals underneath and inside the wreckage.

Image caption The BBC team believe they are the first film crew to dive the Torrey Canyon wreck

I used the big surges to drive me forwards and then I held on during the backwash so I made good fast progress around piles of machinery, winches and twisted steel plates all completely camouflaged with weed, anemones, briozoans, starfish and colourful urchins.

There was no single identifiable cause for the world's largest super tanker to run aground on the well-known and well-charted rocks.

But at time of the disaster the skipper had plotted a shorter than normal route, in effect cutting a corner, and it was the ship's cook who was on watch in the bridge.

There was widespread confusion about how to deal with massive spill. The case has been recently likened to the Deepwater Horizon oil rig disaster in the Gulf of Mexico, which killed 11 people, and resulted in 4.9m barrels of oil being discharged, threatening marine life and hundreds of miles of coastline

A decision was made at the time to bomb the wreck and its oil slick in an attempt to burn the oil.

The Royal Navy were rallied and they led the bombing runs dropping 62,000lbs of bombs, 5,200 gallons of petrol, 11 high-powered rockets and an undisclosed amount of napalm on the wreck and the surrounding waters, sinking the ship, but not really dispersing the oil.

On my dive, as I whizzed round the corner of the superstructure I hovered over one of the many bombs that had been dropped on her.

Image caption The Torrey Canyon's skipper had plotted a shorter route and the cook was on watch when it grounded

I was relieved to see that it had exploded, but it was a healthy reminder that there are hundreds of unexploded bombs on and nearby the wreck.

The 20-mile long oil slick reached the Cornish coast in a few days triggering a massive environmental catastrophe including the death of over 25,000 sea birds.

The familiar golden sand beaches were totally black and no life existed on any of the sea cliffs.

In spite of cleaning car tyres and workers boots, the heavy black crude made its way into the streets, shops and homes.

The fumes could be smelt throughout Cornwall and with the bombers flying low making their runs to the wreck site one could be forgiven for thinking that a version of black hell had arrived.

There was a dire need to "do something" and so a huge clean up operation began including widespread use of detergents. These were such aggressive chemicals that many of the beaches and cliff areas still show signs of their effects.

Six months after the spill some untreated beaches had returned to a pristine condition, whilst the treated beaches had become a wasteland.

Nineteen days after the wreck, its massive oil slick hit western Guernsey and in a reaction similar to the Cornish the authorities decided to act fast.

Tourism was the island's main source of income - the beaches had to be saved.

Image caption The wreck is almost unrecognisable as a ship but the area is teeming with sea life

So in a desperate, fast and furious 11 days they managed to scour the beaches clean by collecting tonnes of the crude and dumping it into a disused quarry. The beaches were saved, but a visit the quarry is a sobering experience.

Much of the oil has been removed and processed for use, but each time a large amount of oil is taken from the quarry, more seeps up from the sediment below and so the process has to start again.

The quarry cannot be dredged to clean it because during WWII, the Germans who occupied the island used it as an armaments dump and tonnes of unexploded ordnance remain. In 2009 the water level rose and the change in pressure released yet more crude from the bottom.

But there is hope - both for Guernsey and for future oil spill clean up campaigns. The Guernsey team are using a process called bio-remediation in the quarry, which uses naturally-occurring bacteria which eat oil as a food source.

These micro-organisms are pumped into the oily water 24-hours a day and it is hoped that in a year all of the oil will have been eaten.

Britain's Secret Seas begins with a programme on the Giants of the West on Sunday 8 May, on BBC Two at 2000 BST.