HD,
It was at something like 3 o'clock of a morning.
'We' were in Lyneham tower, Cotswold Radar was closed at the time so there was nobody else along the route except 'us'.
As a Master Diversion Airfield we had a red 'bat phone' straight thru to D&D at West Drayton and we were on the bat phone quite a bit that night, I recall that all other possibilities had drawn blanks thus it was D&D that instructed us to instruct the 'Mayday'.