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[Weatherlawyer]

In October, Prof John Burland from Imperial College London oversaw the building of the [Palace of Westminster] car park, said the tower was leaning, but it would not be a major concern for at least 10,000 years.:

"There's no such thing as an old building that isn't cracked. In fact they're beneficial because the building moves thermally more than is caused by the Jubilee Line and the movements concentrated around the cracks and, if they didn't, there'd be cracking elsewhere."

Moves thermally more that is caused... what?

Sounds more like no major cause for concern is going to get anything done on my watch. IIRC (I appreciate the tower isn't a brick or stone structure) but:

If the building moves past half a brick's thickness, it is dedded.

Any ideas how that applies to cast iron?

[David Paste]

I take that to mean that the cracks have appeared as a result of thermal expansion / contraction, and this thermal movement is more than any movement caused by the (building of? operation of?) the Jubilee line (which I presume is underneath, or thereabouts, the tower).

But as to what it all means in a practical setting, I dunno, I'm not an engineer, why are you asking me?! :D

[Onetap]

Yes, Jubilee line extension, involved the excavation of a ginormous pit and the construction of retaining walls at Westminster Underground station just over the way. It was in the press and on TV when it was going on.

[Jim Chisholm]

I seem to remember something about 'the middle third rule'. As long as the centre of gravity does not lie outside the middle third of the base a masonry structure is safe (wind loading excepted)

The tower of Pisa was still standing with a far more significant lean!

I suggest playing with a box of children's bricks to get a better understanding of the issues.

Jim