THE proposed sale of New Scotland Yard means the Metropolitan Police will have to find a new home for a macabre collection seen by few outsiders

IT is arguably the most fascinating exhibition in London, all the more so because none of it derives from speculation or supposition. Every one of the exhibits is 100 per cent authentic - no facsimiles here - and the stories behind them genuine and thoroughly documented.

And what stories. The Acid Bath Murderer, The Great Train Robbery, Jack The Ripper, the notorious Krays. People would be queueing round the block to get in.

But they are not because the Black Museum (or the Crime Museum as it is now more commonly called) at Scotland Yard is not and never has been open to the public. Whether that changes depends on where, when or indeed if the headquarters of the Metropolitan Police move to new premises.

If as has been mooted the Met sells off New Scotland Yard and moves to a smaller base to save money, will the Black Museum go with it? A spokesman says: "The only honest answer is, nobody knows. No formal decision has yet been taken about a move so we can't speculate on any other related decisions."

Currently the museum is housed in room 101 at New Scotland Yard, an L-shaped space crammed with glass display cabinets containing the tools and trophies of murder most foul - and other crimes - from the past 150 years.

There are weapons disguised as walking sticks, umbrellas, furniture parts and even a briefcase. This last item belonged to the Krays and was designed to fire a poisoned dart into witnesses as they entered the Old Bailey. It was never used.

One exhibit consists of two plastic bags, one containing a sawn-off shotgun, the other a table leg; the challenge is to distinguish which is which as they look more or less identical.

The oldest item is a pair of handcuffs used in 1841 to restrain a mutineer and one of the most recent is the fake De Beers diamond from the Millennium Dome raid in 2000 which was foiled by the Flying Squad. There is also a letter to "Dear Boss" from 1888 signed by "Jack the Ripper" - the first time the soubriquet was used.

HANGED in 1910, Dr Hawley Crippen, is considered to be the first criminal to have been caught with the aid of wireless communication. After killing his wife Cora and burying her body in the cellar of their home in Camden, north London, Crippen and his lover Ethel Le Neve boarded the steamer SS Montrose bound for Canada with Le Neve disguised as a boy. But the captain became suspicious and sent a telegram to London. A Scotland Yard detective caught a faster ship which arrived in Quebec ahead of the Montrose and arrested Crippen and Le Neve.

MYSTERY: But despite the key role of the new invention, the piece of evidence which condemned Crippen was a fragment of cloth from a pyjama jacket that police found with Cora's remains. It is on display in the Black Museum along with the spade used by Crippen to dig his wife's grave and by the police to unearth her remains.

Serial killer John Haigh, who was hanged in 1949, was known as the Acid Bath Murderer but in fact he used neither a bath nor acid to kill his six known victims. Rather he clubbed or shot them and then dissolved their bodies in a large oil drum into which he poured concentrated sulphuric acid. The 40-gallon oil drum, along with the protective apron Haigh wore, are on display along with three human gallstones which the eagle-eyed pathologist spotted among the gravel stones at Haigh's workshop. The gallstones belonged to wealthy widow Olive Durand-Deacon, Haigh's last victim.

In 1953 John Christie was hanged for the murder of his wife though he confessed to killing seven women in all and hiding their bodies behind Ripper' the walls and in the garden of his home at 10 Rillington Place in London's Notting Hill. One of the exhibits is the item which exposed him as a necrophiliac: a Golden Virginia tobacco tin which contained pubic hair cut from his victims.

as a necrophiliac: a Golden Virginia One of the most inoffensive looking displays is a cooker with a pan on the hob. It is also one of the grisliest for on this stove serial killer Dennis Nilsen boiled up the dissected bodies of the 15 men he had strangled or drowned at two addresses in north London between 1978 and 1983. Nilsen poured the resulting brownish sludge down his drains and a sample of this is on view in the museum.

The ordinary gentleman's umbrella on display is the one with which a mystery assailant stabbed Bulgarian dissident Georgi Markov in the thigh (apparently accidentally) as he walked along London's Waterloo Bridge in 1978. Markov recalled feeling a pricking sensation in his leg as he saw a man drop an umbrella before getting into a taxi. Three days later he was dead.

STRICTLY speaking, the museum is not a museum but an educational resource, part of the Met's Crime Academy. It was established in 1874 following a change in the law which allowed police to keep the property of convicted criminals. An Inspector Neame felt that such material could be used to teach officers about how criminals operated.

Glass cabinets house a large collection of death masks of felons executed by hanging (the mark of the ligature is visible). These were made so that the police could study the lumps and bumps on the skull which the Victorians believed were the indicators of a deviant person.

The collection is still used for training today though everything about its presentation suggests a museum. Hangman's nooses are just inside the entrance, including apparently the rope used to end the life of Ruth Ellis, the last woman to be executed in Britain. However, bloodstained overalls worn by PC Keith Blakelock who was stabbed to death in the Broadwater Farm riots in 1985 have been removed.

Though visitors were permitted in the late 19th century, admission now is limited to police officers from any force and occasionally academics (by prior appointment). Even the identity of the custodian is a secret, although the salary isn't: it's 26,000.

If the Met is looking for ways to boost its budget it could do worse than throw the doors of the Black Museum open to the public. In this instance, crime would pay.