Only an eleventh-hour intervention by a solicitor prevented Ljubinko - a deserter from the Serbian army - from being put back on a flight to Budapest, through which city he had travelled to England.
His solicitor, Susan Sutovic, said that but for her intervention the man's deportation would have gone unnoticed and unrecorded.
There also appeared to be a confused policy at Heathrow earlier this week, when a student, Tatjana Leudar, 20, arrived from the troubled republics.
She intended to start a 12-week language course in London - it was fully paid for and she had arranged accommodation.
When officials discovered her boyfriend was already here as an asylum-seeker, they refused to allow her entry.
Instead she applied for asylum and was allowed into the country while her application - which could take up to two years - was considered.
Ljubinko, 21, from southern Serbia, had tried to enter as a visitor at Heathrow on Wednesday, hoping to join his brother, already seeking asylum in London. He told his lawyer he had been questioned at Heathrow for 10 hours before officials decided not to allow him entry and to serve him with a deportation notice.
Ms Sutovic's call came with just 50 minutes to spare before he was to be flown out. He has been given temporary admission to seek asylum. 'He had spent a lot of his money getting here. All that would have been in vain had he been sent back,' Ms Sutovic said.
Yesterday a Home Office spokeswoman emphasised it was not government policy to allow in everyone from the former Yugoslavia - some areas were not troubled by war.
She said that immigration officials at Heathrow were not satisfied Ljubinko was a 'genuine visitor'.
They had decided to deport him only after asking him if he feared being returned to either Hungary or the former Yugoslavia and he had said he did not.
Lawyers have said that despite government claims that 4,000 former Yugoslavs were entering Britain each month, many like Ljubinko have been turned away at airports and ports. A political storm blew up this week when it emerged that 36 asylum-seekers had been deported and that ministers had rejected a plea from the United Nations High Commissioner for Refugees to stop its deportation policy, in the spirit of sharing the international burden caused by refugees fleeing the war zones.
On Wednesday, Charles Wardle, Under-Secretary of State at the Home Office, defended those 36 deportations, which his department had said were carried out within the 'spirit' of the Dublin Convention.
This is an agreement which means in effect that refugees can only claim asylum in the first country to which they flee, signed in 1990 by all 12 European Community governments.
Mr Wardle did say that the practice would be eased for those Yugoslavs who had not lingered in other countries and who had contacts here.
But Louise Pirouet, co-ordinator for Charter 87 for Refugees, was critical of the convention, which meant those deported had no right of appeal to any court. 'Law which cannot be tested in any way is bad law,' she said.
The Home Office said that yesterday 30 Yugoslavs were admitted at Heathrow to pursue asylum claims - two of whom had been rejected by Germany.