I've been wracking my brains Mal and i've always thought it was 1984 when they launched the diesel Rangie, about the same time or just after the SD1 got the VM 2400 turbo diesel to make the 2400SD but i could well be wrong.
Rural owners loved them as they could often get away using the same fuel as their tractors

especially in the early days before the ruse became more widely known.
Just hit on the idea of Wikipedia and it was 1986 - you were spot-on! They had been trying to "dieselise" the V8 engine but it failed :
From 1979 onwards, Land Rover collaborated with Perkins on Project Iceberg, an effort to develop a diesel version of the Range Rover's 3.5 litre V8 engine.[12] Both naturally aspirated and turbocharged versions were built, but the all-alloy engine blocks failed under the much greater pressures involved in diesel operation. The project was, therefore, abandoned. The effort to strengthen the Rover V8 for diesel operation was not, however, completely wasted; the 4.2 litre petrol variant of the engine used crankshaft castings developed in the Iceberg project.[13]
Because of the Iceberg failure, it was not until 1986 that Range Rovers gained diesel engines from the factory. The more efficient 2,393 cc (2.4 L; 146.0 cu in) inline-four VM diesel from Italy was made available as an option for the heavily taxed European market as the 'Turbo D' model,[6] and were increased to 2,499 cc (2.5 L; 152.5 cu in) in 1989.[10] The VM engines were highly advanced and refined diesel engines for their time but were received poorly by the UK press, who tended to compare their performance to the V8 models. To counter these criticisms Land Rover used a Turbo D Range Rover to set several speed and endurance records for diesel vehicles during 1987, including a continuous run over 24 hours at over 100 mph (160 km/h). The VM were replaced by Land Rover's own 200Tdi turbocharged diesel engine in 1992.[6] and 300Tdi at the end of 1994.
From :
https://en.wikipedia.org/wiki/Range_Rover_Classic
A diesel-fuelled 4.2V8 would have been quite an animal!!!
