The men's room at the Butlin's-operated Top of the Tower restaurant was the site of an October 31, 1971 bombing by the Angry Brigade and by 1980 the restaurant had closed and in 1981 tower was closed to the public.
Now called the BT Tower, it is England's fourth-tallest building.
Last year the tower was open — for one day and to only 480 people as part of Open House London.
There were plans to reopen the restaurant at the end of this year but BT decided against it.
The GPO Tower was toppled by Sparkle the kitten in the "Kitten Kong" episode of The Goodies which originally aired about two weeks after the bombing.
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Vintage "Certificate of Orbit" given to restaurant patrons.