Contractor for Elizabeth Tower’s main £29m restoration contract to be appointed in the autumn

Big Ben’s famous bongs will sound for the last time in four years on Monday 21 August at noon, to allow major conservation works to be carried out.

The Elizabeth Tower, home to the Great Clock and the 13.7-tonne Great Bell – popularly known as Big Ben – is undergoing a complex programme of renovation work.

Sir Robert McAlpine was appointed last November for the £3.5m preconstruction contract, which involved assembly of scaffolding around the tower. A contractor for the main £29m restoration contract is due to be appointed in the autumn.

The conservation project began earlier this year. Once the scaffolding has been erected to the necessary height, work will begin at the top of the tower with the renovation of the Ayrton Light - which shines to show that Parliament is sitting - and the refurbishment of the cast iron roofing.

The team will then work their way down the building, removing the scaffolding as the restoration work progresses.

The Great Clock itself will be dismantled piece by piece and each cog restored. The four dials will be cleaned, the glass repaired, the cast iron framework renewed, and the hands will be removed and refurbished.

During this process, it will be necessary to cover the clock faces, though one working clock face will remain visible at all times throughout the works. The scaffolding is expected to cover three of the four clock faces by the end of October 2017.

As the clock mechanism itself will be temporarily out of action, a modern electric motor will drive the clock hands until the Great Clock is reinstated.

Steve Jaggs, Keeper of the Great Clock, said: “Big Ben falling silent is a significant milestone in this crucial conservation project. This essential programme of works will safeguard the clock on a long term basis, as well as protecting and preserving its home – the Elizabeth Tower.”

Big Ben’s bongs last fell silent for maintenance in 2007, and prior to that between 1983 and 1985 as part of a previous large scale refurbishment programme.