The site on the Weighbridge is undergoing a £22-million redevelopment and a larger hotel is scheduled to open next April.
The significant development is funded completely by private investment.
The existing building has been open every day since the 1830s but on Saturday the bar will close for the last time signalling the end of the old business for good.
To mark the occasion, the mother of owners Mike and James Taylor, Edith Taylor, and the hotel’s longest serving employee Moises Varela enjoyed the final meals served in the London Grill yesterday.
Mr Varela, a barman has worked for the Royal Yacht for nearly 32 years having started in October 1974 and will now be retiring.