Many vehicles used by Civil Defence, AFS etc had pairs of amber lights housed in a 'rounded end' rectangular box mounted on the front — on Bedford RLs (and similar) they were centrally above the windscreen, but on Land-Rovers they were fitted to the leading edge of the bonnet. This was incompatible with carrying a spare wheel on the bonnet, so the wheel was moved into the back of the vehicle, clamped upright to the bulkhead.
Generally these light units were not kept when the vehicles were demobbed, and I can't at this moment lay my hands on a suitable photo to illustrate. It does, however, give a pointer to the possible Home Office origins of a vehicle — if it has unexplained holes in the leading edge of the bonnet, then it possibly carried amber lights... but the absence of holes doesn't say the vehicle is not Home Office.
Their purpose? I always thought that they were some form of convoy lighting, but correspondence with Dave Price suggests that the two lights would flash together as a pair as a form of emergency vehicle warning — a forerunner of the blue lights used by UK rapid response vehicles nowadays. If anyone can shed further light (!) on this, please email me on firstname.lastname@example.org.
Mike Mason wrote (12/06) to say that amber lights were fitted to the front of AFS (only) Land Rovers and Austin Gypsies. He says that (contrary to what I understood above) there was more than enough room on the bonnet for the lights and tyre! He sent a pic (of RGC589/KVS613) to prove it.