According to civil engineers, Big Ben* is having some trouble maintaining its erectness: the tower is lurching ever so slightly to the northwest, and the lean is now visible to the naked eye.
Speaking to the Sunday Telegraph, John Burland, a senior research investigator from Imperial College London, claimed that the lean can be seen if one stands on Parliament Square and look towards the river. "I have heard tourists there taking photographs saying ‘I don't think it is quite vertical' – and they are quite right", said Mr. Burland.
The apex of the tower, completed in 1858, is now leaning 1.5inches northwest from the vertical position, at an angle of 0.26 degrees; by way of comparison, the famed tower in Pisa leans four degrees and 12ft off the vertical, so no need for MPs in Portcullis House, which is in the path of Big Ben's eventual collapse, to concern themselves just yet.
The tower's proximity to the river, and decades worth of subterranean work in the area (as amply demonstrated in this diagram) have undermined the foundations and caused the lean. There was particular concern during the tunnelling of the Jubilee line extension that engineering work could affect the tower's stance; Ian Visits has a wonderfully detailed report from a talk at the Royal Society about the challenge of keeping Big Ben erect (Ian's also neatly rounded up how the media have reported this story, focusing on what misleading images they've used to illustrate the lean; our own effort above carries a suitable warning label).
Photo / wallyg