20 Fenchurch Street is a development which includes a new 36-storey skyscraper, nicknamed the Walkie Talkie. The previous building on the site had been constructed on under-reamed pile foundations with a single level of basement. The new building formation level is significantly deeper than the original,  and so the original under-reamed piled foundations were assessed to have little usable capacity. Piles for the new building had, where necessary, to be threaded between the existing pile under-reams; the new piles were designed such that they were entirely in the London Clay, making them considerably more economic and faster to install than if they had to penetrate into the deeper strata.