Big Ben's lean accelerating

LONDON, Oct. 11 (UPI) -- London's Big Ben tower is tilting at an accelerated pace due to shifts in the ground and tunneling underground for Tube lines, a study found.

Engineers have been aware for years of Big Ben's lean, but a survey done by the London Underground and the Parliamentary Estates Department found the rate of the tilt has increased. The lean has caused the walls of the House of Commons to crack.

The 315-foot tower moved 1/8 of an inch between November 2002 and August 2003, and the angle has increased by 0.04 of a degree yearly since then, London's Daily Mirror reported Monday. In total, Big Ben's peak is about 18 inches off where it should be if vertical, about 1/16 of the lean of Pisa's tower.

"I have heard tourists saying, 'I don't think it is really vertical.' They are quite right," said John Burland, a professor at Imperial College London. "The tilt is now just about visible. If it started greater acceleration we would have to do something in a few years."