He confessed during a debate on the Road Safety Bill, adding that they were "perfectly legal".
He was responding to his Conservative counterpart, Owen Paterson, who also has such a device, claiming that made him drive more safely. Mr Paterson asked: "Could you clarify that those devices, which just say where these cameras are positioned, will continue to be allowed." Mr Ladyman said: "They will continue to be legal and I have got one myself."
Mr Paterson replied: "I am delighted that there is cross-party consensus on this issue."