Network Rail engineers have installed a giant, 30m-long signal gantry as part of the London Bridge station revamp.
The works took place over last weekend, when the site team had an extra hour due to the clocks going back.
The new gantry spans 10 of the 11 tracks on the approach to London Bridge station.
Network Rail is completely rebuilding London Bridge station over the next three years as part of the £6.5bn Thameslink Programme.
Over the Christmas and New Year period, parts of the station will be closed for 16 days to allow engineers to finish the job by attaching new signalling equipment. The current system has been in use since the 1970s.