Adding The Extra Second To Big Ben

It is especially important that Big Ben chimes on time because as well as bringing in the new year across the Nation, it will be heralding its 150th anniversary.
Old pennies help keep the Big Ben's Great Clock precisely on time

The Great Clock, which dictates when Big Ben bongs, keeps its time with a swinging pendulum.

The pendulum can be adjusted by adding or removing weights that sit on top of it - weights that include old pre-decimal pennies.

By removing one, the clock slows down by 0.4 seconds over a 24 hour period.

Throughout the evening, the men who look after Big Ben, known as the Westminster Clockmakers, will be removing pennies to ensure that the bongs bong precisely on time.

According to the Keeper of the Great Clock, Michael McCann, there is no margin for error. He says the world is looking to Big Ben to get it right because of its iconic status.