A week or so ago I was over at Buckland Abbey – to get there you have to cross Roborough Down on which is located a very large rock / Tor known as Roborough Rock. It is perhaps the easiest of all the Tors to visit as it is right beside the road by a car park!
All around the Rock and the Downs there are the remains of RAF Harrowbeer which was constructed as a Second World War fighter station for the air defence of Devonport Dockyard and the Western Approaches. Spitfires, Mustangs, Naval rescue and naval attack planes were all based at some point at Harrowbeer.
Roborough Rock was located at the end of one of the runways and apparently there was talk of blowing it up as it was a hazard to aircraft.
70 years on the Rocks remains and the fighter station has gone – it think that is the right way round.
A Dartmoor blog 
Roborough is probably ruh beorg – Rough Hill.
Hansford Worth gives an earlier alternative of Udal Tor for the rock.
I have also seen references to “Yelverton Rock” (Eric Hemery, on a map in his “Waterways” book) and to “Duke of Wellington’s Nose”, which Tim Jenkinson says is a name used locally.