Stamford Street will be closed to eastbound traffic for three weeks starting this weekend.
Southern Gas Networks will be carrying out works at the eastern end of the street.
The eastbound road closure begins on Sunday 8 February and continues until Monday 2 March.
Buses RV1 and 381 will be diverted via Waterloo Road, St George's Circus and Blackfriars Road, adding three quarters of a mile to the route.
The lengthy diversion will put extra pressure on bus services which are already being used by more passengers than normal due to the part-closure of London Bridge Station.
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