The various boxes on the former L&SWR main/Windsor lines out of Waterloo must have been quite heavy after their roofs were armour plated as an ARP. Unfortunately someone forgot to remove it after the war ended with a predictable result.
The late Micky Sellars used to tell the story of how (as Shipping & Port Manager at Newhaven) he had to meet the Southern's Chief S&T Engineer off the afternoon boat arriving from Dieppe with the message that he was required to report immediately to the GM because "Clapham Junction A box had collapsed". Having been told to pull the other one, it's got bells on it, Micky produced an early edition of the Evening Standard with a photo of said box filling much of the front page - apparently the absolute look of incredulity on the man's face had to be seen to be believed.
It says a lot for the inherent professionalism of the bobbys in the box that they found time to put everything back and to send 6 in every direction before fleeing the floundering box.