Vauxhall Cross, which has featured in several James Bond films, opened as the MI6 headquarters in 1994

The Secret Intelligence Service could be forced to overhaul the layout of its London headquarters if evidence emerges that misplaced floor plans have fallen into enemy hands.

A building contractor was sacked from renovating Vauxhall Cross after losing sensitive files about a fortnight ago. Balfour Beatty workers misplaced about 100 documents detailing the layout of the distinctive site by the Thames. They are thought to have contained the location of alarms, stairwells, electrical cabling and the precise placement of desks and specific offices.

The blunder has caused fury in Whitehall and is being treated as a gross security breach. The lost information is viewed as highly valuable to malicious actors. A review of MI6’s relations with contractors will be launched with strict security protocols around