The Bomber Command war memorial that was defaced has now been covered up and has a police guard.
Douglas Radcliffe, Secretary of Bomber Command Association said that the airmen honoured in the Bomber Command Memorial had died to give people the freedom to live in the UK.
He added: "I can't believe that somebody would do this but they've done it."
The Bomber Command Memorial in central London has been defaced. It is dedicated to the 55, 573 airmen who died in the Second World War. This figure includes 25,000 men from Lincolnshire air bases.
Reports are coming in that the Animals In War Memorial in Park Lane has also been defaced. More details to follow.