The Millennium Bridge in London will be closed for three weeks for urgent maintenance work after parts of its underside started to degrade. The suspension bridge, also known colloquially as the “wobbly” bridge, crosses the Thames and links St Paul’s Cathedral in the City of London with the Tate Modern gallery on the South Bank. It will close to pedestrians from 8am on Saturday 14 October while workers replace the synthetic membrane that separates the bridge’s steel structure from its aluminium bridge surface, or deck. Giles Shilson, the chair of the City Bridge Foundation, said the bridge was beginning to deteriorate as a result of years of wear and tear, and that damage to the layer under the bridge’s surface needed to be fixed. “Since it opened to mark the new millennium, the bridge has become a much-loved and very well-used fixture on the London landscape, but it is starting to show its age,” he said. “The separation layer under the bridge deck has started to degrade, which means it’s having an adverse effect on the bridge deck and needs addressing urgently. “Replacing this layer is a time-consuming process, meaning we have no option but to close the bridge for three weeks and to work round the clock to get it done as quickly as possible. “We’re sorry for any inconvenience but hope people will understand we do need to do this work, and will see the benefits after we give the bridge a much-needed deep clean that will leave it looking as good as new.” The 325-metre-long (1,066ft) bridge is one of five owned and maintained by the City Bridge Foundation. It is planned the bridge will reopen to the public on Sunday 5 November at the latest. Work will take place 24 hours a day. Signposted diversion routes for pedestrians will be in place via Southwark Bridge and Blackfriars Bridge. The bridge was closed shortly after it first opened in 2000 because of unexpected swaying and vibration problems as large numbers of people crossed it. The bridge was fitted with shock-absorbing dampers to reduce its lateral movement to a safe level, before reopening in 2002. A study by the University of Bristol in 2008 found that pedestrians walking randomly and keeping balance as normal can cause bridges to sway, which challenged previous theories that the “wobble” was due to pedestrians synchronising their footsteps with the bridge’s motion.