Mad Jock:
I visited D&D at West Drayton about a year ago and was suitably impressed. They made the point that they do welcome Practice Pans.
So, travelling back from Ireland to Kemble via Haverfordwest we decided to put it to the test. About 30 miles east of Haverfordwest at F055 or F075 (I forget which), we called for practice pan, simulating lost. We were given a squawk and the position fix came quickly and was verified as accurate by GPS. With D&D's permission we continued the simulated emergency by requesting vectors for Swansea. Over the next ten minutes, we were vectored exactly overhead the airfield with increasingly small and frequent heading changes as we got closer. Final position was spot on, confirmed by looking down. D&D used radar, I think the feed was from Clee Hill. If I remember correctly, they can switch-in feed from any one of many radar heads, giving tremendous flexibility,
Had we really been lost and needed help to find the airport, it would have been very easy for the pilot. No doubt the same result could have been achieved at many radar units, although I'm not sure how low we could have operated and still be given vectors.
AA.