The body - reference number DB14/92 - was washed up on 24 March last year. The eyes, fingers and skin had dissolved. The man was about 50 years old, 6ft tall and probably homeless. Police have since been trying to identify him in a search that has cost an estimated pounds 5,000.
The bloated bodies recovered by police trawlers are towed to Wapping, east London, in a body bag in the water for fear of disease. They are photographed at once as the corpses blacken in the air. They are then searched and the discovery publicised.
The case of DB14/92 alone has absorbed hundreds of police hours. As there is no possibility of taking fingerprints an expert has spent weeks reconstructing the face using clay moulded on to the skull. A forensic dentist has examined the teeth and details have been compared to hundreds of missing person profiles. The blood has been tested for drugs and alchohol. The clothing has been traced and the man's only possession - a gold 1978 Timex watch - sent to its maker. But the body remains unidentified. It is the Wapping identification unit's first failure. PC Peter Clements was its first appointment; his first day in office coincided with the Marchioness disaster in August 1989 in which 51 people died.
Until the case of DB14/92, the unit - which was created to identify and trace relatives of the 50 or so corpses recovered from the Thames each year - had had a 100 per cent success rate. But that case was followed by the discovery of three other bodies which have so far also eluded identification.
PC Clements believes this is because more homeless people than usual died in the Thames last year. Homeless people are notoriously difficult to trace. They own little and their friends may not read the newspapers where appeals for information are printed. They are usually not reported missing. Most recent figures show that of 35,970 people who went missing in 1991-92, 1 per cent were found dead.
Many who took their own lives had tried to avoid being named. Others, the victims of crime, had had identifiable possessions removed. There are about 70 attempted suicides in the river a year.
PC Clements will soon accept that at least two of the corpses will not be identified. When they are buried they will lie in unmarked graves, their details filed only under burial plot records.
Police attempts to trace them will have cost pounds 10,000. The four, undoubtedly the object of more state care and expense dead than alive, will return to obscurity.