Big Ben

The work has seen the 96-metre-tall Elizabeth Tower, one of the most photographed buildings in Britain, enveloped in scaffolding for the last two years as the four clock dials are reglazed, ironwork repainted and intricately carved stonework cleaned and repaired.

In March, part of the scaffolding was removed, showing that the clock's once black numerals and hands have been repainted blue, in line with what scientists say was its original colour.

Officials say the famous clock at Britain's Parliament — used by Londoners for decades to check the time — has recently been slow by as much as six seconds.

The 156-year-old clock chimes every 15 minutes and emits deep bongs to mark the hour. Its inaccuracy was noticed by staff at BBC radio, which broadcasts the bongs live at 6 p.m.