In March 1973 I was called on to do a 'lone ranger' from Odiham to Practica (Rome) via Cognac and Istres. All the RAF Pumas had as a nav aid at the time was Decca Mk8: 3 dials plus a master and a roller map that was initiated manually. Like all hyperbolic nav systems the accuracy deteriorates the further you get from the transmitters and Decca effectively ground to a halt half way down France.
After that we had two problems; one was transiting all the controlled airspace on the French Riviera and the sea crossing from Nice to Cape Corse in Sardinier.
Not having even an NDB when we were asked to report over a beacon we would look up the beacon; plot it from its Lat/Long on our 1/4 million; DR towards it and call overhead when we got there. We did this fast and accurately enough for nobody to raise any comment.
For the sea crossing we borrowed a drift sight. This had a plumb edge to it and on the Puma you could raise the centre panel to mount the load pole. The back of the was perpendicular to the aircraft's centreline so by mounting it against this and looking through it at the sea you could ascertain your drift. An accurate calculation of TAS plus three timed changes of heading and with a whizz of the Dalton you had your track and groundspeed.
IIRC we put in three corrections of heading and we hit Cape Corse on track within 45 seconds of the last ETA.