It was W.B. Yeats's express wish that he be buried at Drumcliffe, Co Sligo, but whether that wish was ultimately granted may be open to question. My late father, the poet and film-maker John Ormond, suspected it was not the body of Yeats buried there and intimated as much in his Picture Post article of October 9th, 1948. Further evidence reinforced those doubts and suggested that the body in Yeats's coffin may be that of Englishman Alfred Hollis.

Consideration for the feelings of the Yeats family and, it would seem, interests of national diplomacy meant that evidence was not published. The story both fascinated and frustrated my father.

A recently published family history by a relative of the Hollis family prompted me to re-examine my father's writings on the subject. Louise Foxcroft's grandmother, Amelia Emery, was Hollis's sister, and Foxcroft's book, reports of which appeared in the London Review of Books and the Guardian, contained accounts of the possible mix-up handed down through her family.

Yeats died at Cap Martin in the south of France on January 28th, 1939. He was buried at nearby Roquebrune in the graveyard of the church of St Pancras, whose black tower he saw from his sick-bed and enshrined in his last poem. The outbreak of war meant that nine years passed before the Irish government could bring the great man back home.

In August 1948, my father, then a staff writer on Picture Post, was sent to France to cover the story of Yeats's return to Ireland. The very assignment was a kind of homage. Just 25 and already a published poet himself, he was a huge admirer of Yeats.

But that sense of honouring a great poet also made him note in the article that he and his colleague, photographer Haywood Magee, were not convinced it was Yeats's body in the coffin that returned to Ireland.

At Roquebrune cemetery, where Yeats's body had been exhumed five months earlier, his original grave was not apparent. The sexton and undertaker had separately shown them two alleged burial spots: the first - its cross dated 1946 - had been used again for burial; the second was an open grave whose background was completely different from that in an Irish Times picture of Yeats's grave published during the war.

On the burial register his name appeared as William Butler, the Yeats omitted. The coffin had seemed in too good condition to have lain in earth for nine years; the name plate on the lid was tarnished but the screws holding it in place were new and shining.

Only later did it seem strange that the Chief of Police rubberstamping their photo permit handed it over on condition that they did not ask for the coffin to be opened. Something else had baffled them too.

Roquebrune's sexton, an old man with a badly cleft palate, recognising the name of Yeats had cried "Ah, Yatts." Indicating a grave, he had insistently repeated a word which sounded like "Ahoo, ah-oo," clasping his waist by way of illustration. Only next day did my father grasp his meaning. In a lingerie shop buying a gift for my mother, the assistant offered him a suspender belt, holding it round her waist, saying "Ceinture tres jolie." The old man had been saying "ceinture". When they checked, he had nodded, beaming broadly at being understood. But as to the significance of this "belt", they were none the wiser.

Back in London, within hours of the article's publication, a visitor awaited my father. Publican Albert Emery had read Picture Post that morning with particular interest. On January 29th, 1939, at Victoria en route for the south of France, Mr Emery, his wife and her brother Alfred Hollis, read in the paper of the death of Yeats in the very place they were visiting. Their holiday was partly for Alfred's benefit - an invalid suffering from tuberculosis of the spine, he was obliged to wear a surgical steel corset - but he died a fortnight later on February 11th and was buried in the grave next to Yeats in Roquebrune.

Eight years later in 1947, Emery went back and was distressed to find no sign of the original graves and all efforts to ascertain where Alfred Hollis's body now lay proved fruitless. The following year, they learned from a press report that the body of Yeats was to be exhumed and taken back to Ireland. How, they wondered, could that be? Albert Emery wrote to Michael Yeats, the poet's son. His reply suggested that Mr Hollis's remains "would be found near where his father's remains had been discovered". A number of graves had been disturbed during the war and the remains removed to an unmarked corner of the cemetery, he explained and, thanks to the French Legation in Dublin, the matter had been dealt with on their behalf by the French authorities.

A sympathetic letter, but Albert Emery saw little hope. He now remembered that the doctor attending his brother-in-law was called Gaston Germont and my father thought this worth following up. He telephoned him.

Yes, said Dr Germont, when the exhumation order had come, the French authorities had been at a loss. Who was Yeats? There was no record of his burial at Roquebrune. As the local doctor they had turned to him for help. During the war when skirmishes between Italian troops and Resistance fighters produced casualties, the angry Italians had dug bodies from the local cemetery, burying their comrades instead. Since the bodies taken from the graves had been buried together in a common grave, identification would be problematic.

But not for the doctor. Two "Englishmen" had died in Roquebrune within a few weeks of each other early in 1939 and he had attended them both. He would always remember the great poet because he had worn a surgical steel corset. It was he who instructed that the body with the steel corset be exhumed. It was my father's belief that, in his mind, Dr Germont had transposed Alfred Hollis's surgical steel corset to the body of Yeats.

Over the years, private speculation continued. The story surfaced again in 1988 when Diana Souhami published her biography of the painter Hannah Gluckstein, known as Gluck. Gluck and Edith Shackleton (Yeats's last lover) had encountered similar confusion when looking for the Yeats grave in 1947. Friends taking up the matter learnt that a steel corset had been a factor in identification and, on learning of the exhumation order, had counselled caution. Writing to The Irish Times Michael Yeats said his family were "satisfied beyond doubt" there had been no confusion, adding that his father had worn a leather truss because of a hernia.

Had DNA tests existed in 1948, forensic science might immediately have offered conclusive proof, but for Amelia Emery's descendants, doubt will linger on. Meanwhile the facts, such as they are, make the final stanza of The Black Tower even more chilling:

There in the tomb the dark grows blacker,

But wind comes up from the shore:

They shake when the winds roar,

Old bones upon the mountain shake.