https://www.theregister.co.uk/2019/09/19/geeks_guide_to_the_central_telegraph_office_and_bt_centre/

Geek's Guide to Britain The BT Centre is an unremarkable-looking building just north of St Paul's Cathedral, nine storeys of Portland stone with straight unadorned 1980s lines softened by curved corners. The headquarters of the UK's largest telco could be mistaken for an apartment block if it wasn't for the company's logo.