Greene King pub the Fort St George on Midsummer Common, Cambridge, has marked a reserved space for the Prince of Cambridge by installing a plaque on the wall above a new highchair fit for a prince. The Duke and Duchess of Cambridge first visited the Fort St George in November when Kate was just a few weeks pregnant, to have lunch by the riverside. Pub manager John Cecchini said: When the world found out William and Kate were expecting we were thrilled, having welcomed them into the pub just a few weeks earlier. Now he is here safe and sound, we want the family to know they are very welcome to come back any time, and there will always be a reserved space for him. The plaque will be a permanent fixture above the reserved highchair, ensuring the future King will always have somewhere to sit on any visit, the pub chain said. Mr Cecchini added: As he gets older, we will make sure the seat under the plaque grows with him. Meanwhile an online book of congratulations has been opened for anyone wishing to send messages to the Duke and Duchess of Cambridge following the birth of their son. Cambridgeshire County Council has opened the online book while further books have been placed in the reception areas of Cambridge City Council, Cambridgeshire County Council and Peterborough City Council. The online book will be printed off, bound and sent to Kensington Palace, together with the hard copies of the congratulations books. Messages can be left online at: http:\/\/www.cambridgeshire.gov.uk\/council\/congratulations Lord-Lieutenant of Cambridgeshire Hugh Duberly CBE said: I would like to extend my warmest wishes and congratulations to the Duke and Duchess on the birth of their baby, the Prince of Cambridge. I am sure many people will want to join me in sending their own personal messages to the couple, and the books of congratulation which have been established across the county will enable them to do just that.