Ian Callum?
Sorry for the slow answer, but I've been traveling for the last 10 days. So yes, this is a design by Ian Callum, sketched in 1968 when he was 14-years-old, and sent to Sir William Lyons at Jaguar for his opinion, which was very positive (and ironic now that Callum heads up the Design team at Jaguar Cars). Another point to you Skut.