Bbadanov,
I certainly did not realise there was originally a fourth ordered. Possibly that jet may have been intended for other things at Bedford or RSRE. More likely, as was common with RAE programmes, someone who knew better than the programme experts scrubbed it to grab the funding for their pet project!
The Tornado programme mentioned was serviced by 2 x Buccardos. We had one at Farnborough after its time at Warton was complete, the Tornado nose certainly improved the aircraft handling most noticeably, it was a joy to fly
lm