Built 1942 as R5014 for the RAF c/n 82909. It's a genuine DH machine and not one of the many built by Morris Motors.
You can get the RAF service record easily enough. I note that the CAA say it wasn't registered as G-ANGM until 1954 but it wasn't (as far as I can see) given an RAF M serial so it must have remained active until that time - or in storage. It was recorded as going to the Torbay Aircraft Museum in 1971.