The firm has seen off rivals including Sisk and ISG for the deal to revamp the world-famous hotel off the Strand.
The Grade II listed hotel, which was first opened by Richard D’Oyle Carte in 1889, will close on 14 December for 16 months.
During the closure Chorus, which is also working on the refurbishment of the Connaught Hotel in Mayfair, is expected to gut the hotel, carrying out major structural works to the River Thames frontage. All of the hotel’s rooms will be overhauled, as well as the reception areas.
One fit-out source said: “The £100 million figure for the refurbishment covers all of the works that are to be carried out on the hotel, not just the main contract.
“But this is still one of the biggest hotel packages to come up in London in recent years and Chorus’s experience at places like the Russell Hotel seems to have put them line for the job.”
Next month auctioneer Bonhams is to hold a three-day sale of furniture, fittings and works of art from the hotel, expected to raise up to £1 million towards the cost of the refurbishment.