Emma Christoffersen died after a long-haul flight

The 6ft 5in forward - a star of the Welsh rugby scene around a decade ago - almost died when the blood clot moved to his lungs six months later.

He will have to take blood thinning drugs for the rest of his life.

Mr Hopkins, 38, from Caerphilly, who now works as a medical rep, said he was taking action against British Airways and campaigning for proper warnings to be given to air passengers about the dangers of DVT.

He suffered the condition on a flight from Australia after watching the British Lions tour last summer.

Just weeks later he started gasping for breath - even walking upstairs at his home left him gasping for breath.

The doctor diagnosed asthma, but when he told a friend about it while out having a drink in Cardiff in January, the scale of the problem emerged.

"He told me to get it checked out straight away so I left the pub, hailed a taxi and asked to be taken to the University Hospital of Wales," said Mr Hopkins.

MP John Smith has campaigned for action

"I told them about my previous DVT and they carried out an ECG.

"They immediately thought I'd had a heart attack."

However, one of Mr Hopkin's main arteries to his lungs was 80% blocked by the fragments of the clot which had moved from his leg.

"My family were told and it was touch and go for a while.

It was incredible to think that I was seriously ill from a long haul flight six months earlier."

Mr Hopkins was treated with an experimental clotbuster and is now trying to rebuild his life - without his rugby which he can no longer play.

"I'm alive and that's what counts," he said.

"I'd hoped to play veterans' rugby but that is out of the question.

A spokeswoman for British Airways said: "Clearly we do sympathise with anyone suffering from DVT.

"As an airline we are keen to learn about DVT.

"It is known to be linked to long periods of immobility and we are trying to find out if it relates to flying per se.

The spokeswoman said the airline provided information for well being in the air, including exercises in seat and warning people to move around.

Mr Hopkins had travelled to see the British Lions

They also have a video showing exercises like pilates.

More than 40 long haul airline passengers are known to have died from DVT clots.

Among them are Emma Christoffersen, from Newport, Susan Mavir-Ross, from Llay in Wrexham, Thomas Lamb, from Cardiff, and policeman John Thomas from Cowbridge, south Wales.

Medical research has shown that clots develop in blood vessels deep in the legs when circulation slows.

The clots can prove fatal if they break off and are carried to the lungs, blocking the flow of blood.

Although claims have repeatedly been made linking DVT and air travel, there is no conclusive proof of the link.

The Vale of Glamorgan MP John Smith has put himself at the forefront of the campaign to get the risks acknowledged.

He is chairman of an all-party parliamentary group set up to investigate the causes of flight-related DVT.

Last month he helped persuade Sven Goran-Eriksson to get the England footballers to wear special stockings - which may help prevent the condition - on their flight to the World Cup Finals in Korea and Japan.