Two stories spring to mind, one personal and the other apocryphal.
I was on exercise on the IGB when my brother was taken dangerously ill. My brother in law, a nice but clueless civvy was given the job of contacting me - we're talking 1980 here - no cell 'phones. All he had was my regimental number and my unit so he calls the MP's in Aldershot at about 1200 on a Saturday afternoon, why Aldershot? - "Home of the British Army" I suppose. By 1400 I was in a Gazelle on my way to Dusseldorf Airport.
The second tale relates to one of the Toms in 1 PARA in Berlin. He hatched a plan with his girlfriend back in the 'Shot whereby she would send him a message that his mum was dying in hospital and he was required at her bedside. Good plan and it seemed to be working as the wheels went into motion, what he didn't realise though is that they check out both ends of the message while they plan for the worst and as he had one leg over the cockpit of a Lightning trainer - this was a while ago - the MP's grabbed him by the collar and he was well and truly lifted!
'CLANG' - watch yer fingers!