A landmark High Court ruling has blocked an attempt by DVT victims and their relatives to sue airlines.

The group of UK families claimed that airlines failed to warn them of the risks of long-haul flights.

The judgement is a victory for the airlines, which faced a multi-million pound bill if the case went against them.

I am satisfied that it is appropriate for the line to be drawn Mr Justice Nelson

But the claimants have been given leave to appeal and can therefore continue their quest for compensation.

It comes just hours after the Australian courts decided DVT victims could sue airlines in a virtually identical case.

The claimants in the UK were bringing a case against 27 airlines.

DVT is a potentially fatal condition in which a blood clot forms and blocks a deep vein, normally in the lower leg.

It can be brought on by long periods of immobility and is often referred to as "traveller's thrombosis".

'No link'

The High Court said blood clots did not constitute an "accident" under the Warsaw Convention. The 1929 treaty makes airlines liable for damages only in the case of an accident.

The airlines said they were protected under the convention from paying compensation for medical problems classed as a "passenger reaction to the normal operation of an aircraft".

Mr Justice Nelson said: "I am satisfied that it is appropriate for the line to be drawn. The line should be drawn now."

A spokesman for BA had said it would resist any claims against it, in the context of advice given by the government and the World Health Organisation that no specific link between flying and DVT had been established.

We may have lost the legal argument, but I still feel we've won the moral argument Nick Balmforth, DVT patient

In Australia ruling, 59-year-old Brian Povey, took both Qantas and BA to court.

He was hospitalised and forced to give up work after suffering an attack of DVT which he blamed on a three day return business trip from Sydney to London.

Mr Povey said the illness was an "accident" as defined by the Warsaw convention, and he said airlines failed to do enough to warn passengers about the risks of DVT on long-haul flights.

The full case - involving some 500 claimants - is now expected to go ahead next year.

Fighting on

Former DVT patient Nick Balmforth told the BBC: "I'm bitterly disappointed. I think we'd all hoped that with the very different Australian judgement that gave us grounds for hope.

"We may have lost the legal argument, but I still feel we've won the moral argument.

"Obviously we will seek leave to appeal, though that depends on raising the finance necessary to appeal."

Ruth Christofferson, whose daughter Emma died from a DVT said: "The airlines have hidden and will continue to hide behind the Warsaw Convention.

"I suppose the law is the law and they had the law on their side to protect them - what did Emma have to protect her? Nothing, and air travellers will still have no protection."

After the ruling, a British Airways spokesman said: "We are pleased that the High Court has recognised the fact that such legal action is unfounded under the terms of the Warsaw Convention.

"British Airways sympathises with all victims of DVT but since the World Health Organisation and the House of Lords agree that there is no evidence of a specific link between flying and DVT any future claims will continue to be resisted."