1971: Bomb explodes in Post Office tower
A bomb has exploded in the Post Office tower causing extensive damage but no injuries.
The blast occurred at 0430GMT on the 33rd floor of the tower and shortly after police received a call from a man claiming that the "Kilburn Battalion" of the IRA was behind the attack.
A senior detective said: "The incident has all the hallmarks of the IRA. The explosives experts feel this was a professional job."
Security at all public buildings is now being stepped up as police fear the start of a wave of terror attacks.
It is believed the bomb, which blew out foot-thick walls, was planted in a toilet on the lowest of the public viewing galleries.
A warning was given and the building thoroughly checked but nothing was found.
General manager of the tower restaurant Guido Edwards said: "We have had about 100 hoax calls in the last five years.
"We inspected the cloakrooms and nooks and crannies and believed the restaurant was safe."