It is currently free to climb the 334 steps of the clock tower containing Big Ben.

BBC: U-turn over Big Ben trip charges

As a mark of respect, the chimes of Big Ben, as the bell and clock tower by the Palace of Westminster are commonly known, were silenced for the duration of the proceedings.

CNN: SHARE THIS

The London Marathon route, which is lined by hundreds of thousands of spectators every year, starts in Blackheath and finishes near Buckingham Palace, passing some of the capital's most recognisable landmarks including Tower Bridge, Canary Wharf and Big Ben.

BBC: London Marathon runners