The Clock Tower, also known as Big Ben, was constructed as part of the New Palace of Westminster following the 1834 fire which destroyed the old Palace buildings. The tower was completed in 1858 and has developed a very slight tilt.
The leaning Tower of Pisa tilts at an angle of 5 degrees. However, Big Ben’s tilt is unlikely to compare with this for another 10,000 years.
Although the clock tower has developed a very slight tilt (0.26 degrees to the North-West to be precise), this is not a new development and there is no evidence that it is causing further damage to the Palace. Experts believe the most likely explanation is that it leaned during the original construction, due to the ground the foundations rested on being uneven.
The tilt has increased very slightly since 2003. In fact, the movements have been so small the instruments used to measure them have had difficulty picking them up.
It is also doubtful whether the tilt is increasing year on year as the report on the tower states "the accuracy of the data is not sufficiently good to be able to clearly identify the true rate of settlement and tilt with great precision".
Palace maintenance manager and Keeper of the Great Clock, Mike McCann said:
"There’s a very slight tilt, which we monitor closely. There’s no need for MPs to worry about their offices. Nonetheless, members of the public are welcome to see if they can detect the tilt, which has been visible for decades."
Further information can be found in the reports by the Parliamentary Works Services Directorate and London Underground.
Image: Parliamentary copyright