Indeed, and when I told the DVLA that my Triumph had a different frame number from that in the V5C I had a surprise (as in, no forward notification) visit from a copper from the local stolen vehicle unit.
He checked the frame number ( he knew where to look, the font Triumph had used and what the format should be) all under a portable U/V light unit and declared it all to be OK, and DVLA then issued an amended V5C.
This was back in about 2007, and things have tightened up since then.