I checked my bag for old grass before my visit to New Scotland Yard

A colleague asked if I would like to join an exclusive tour around the "Black Museum" at New Scotland Yard, and the word "yes" fell from my lips, despite my being in the dark as to what a "black" museum was. I couldn't believe I had agreed to enter the Met's headquarters voluntarily: in north London, distrust of the police rushes through our systems like sewage on a rainy day. One friend advised me to "make sure there are no old bits of grass in your bag, Lauren. Don't tell them anything."

On Wednesday morning, I shuffled into the Victorian-styled Crime Museum at New Scotland Yard, along with half a dozen other lucky "guests". The "Black Museum" is where the Met stores weapons from all the highest-profile murder cases. It was renamed many years ago, for obvious reasons.

Bag search, through a lift, up some stairs, down a neon-bright corridor and through an anonymous door. Faux gas lamps flickered, and the creamy walls shone with the metal of lethal weapons. The table in the centre of the room held a butcher's display of long blades and machetes. Benches along three walls displayed gadgets straight out of 007's briefcase. My hands involuntarily wandered towards the shiny objects, a "lighter", an innocent-looking "umbrella".

"Don't touch anything!" barked our guide. "They are not what they seem and visitors have been hurt before." He skilfully reassembled the long, black umbrella into a powerful shotgun. Stroking a small black case the size of my palm, he flicked out a violently sharp blade. He turned it over and pointed to a tiny trigger. Someone asked where you could buy one. There were quiet giggles when we were shown the legend "Made in China".

The Crime Museum is hell's waiting room, the devil's own doll's house, filled with his little toys and populated by the screams and bodies of the innocent. Do I sound hysterical? Sorry about that; it's just that it has taken me the best part of a week to resume sleeping at night. Every item we saw had killed, dissected, gashed or maimed someone. Our guide was overly generous with the details: "They say she was still alive after the flesh had been removed" was his favourite phrase. The atmosphere was claustrophobic, dizzying. "This sword still has a police officer's blood on it." He held up a katana: "Can you see?" We could.

In one corner swayed ten hangman's nooses. The central noose had been used on Ruth Ellis. Alongside an elaborate display of smashed and fractured skulls dating as far back as 1918 was Ellis's gun. I started to feel panicky. I tried to shallow-breathe.

Things got worse. We left the small, gothic chamber and entered another room, in which the centrepiece was a white, grimy bath, a stained cooker and a hob complete with its own cooking pot and carving knife. "These belonged to Dennis Nilsen, Britain's biggest serial killer to date." The guide picked up the knife and brought it so close that I backed away, and flinched. "In that glass case are the actual pieces of flesh found rotting in his pipes." Directly in front of me, three red/grey triangles of meat sat glowing in a glass case.

That was it. My mind started spinning. What were we doing here among this maniacal memorabilia? We were peeking, peering, leering at a thousand car crashes, three World Trade Centers, two hundred Sarah Paynes. I turned away, trying not to gasp, faint, retch, and found myself facing a pair of forearms preserved in formaldehyde.

Our grimly jovial guide explained that they were a German officer's idea of a joke. "A murderer we'd been hunting died in Germany. We needed to verify it was him, so the British police asked the Germans to send us his fingerprints. That's what we got."

I sat down heavily and later was given water by concerned senior officers. Their Crimewatch reassurances that most people are quite nice have not removed the smell from my clothes, or the images from my mind's eye.

This article first appeared in the 03 December 2001 issue of the New Statesman, Who needs 12 when one will do?