While the Mirage IIIV is commonly viewed as being more politically palatable due to an emphasis having been placed upon multinational development and manufacturing plans, the design of P.1154 (which only used a single engine) was seen as more straightforward and reliable.

One of the two prototypes constructed was destroyed in an accident; shortly following its loss, the whole project was abandoned; the surviving aircraft has since been placed on public display.

[3][4] Victory in this competition was viewed being of a high importance at the time as it was seem as being potentially "the first real NATO combat aircraft".

[2] NBMR.3 attracted a total of eleven contenders, including Dassault's Mirage IIIV proposal, which would become viewed as the principal competitor to the P.1154.

[7][2] While the P.1154 was judged to be technically superior, the Mirage IIIV had acquired a greater level of political palatability due to the co-operative development and production aspects proposed for the programme, under which work was to be distributed across a number of member nations.

[7] According to aviation author Jeffort, the Mirage IIIV was rejected mainly because of its excessive complexity: using nine engines, compared to the P.1154's single-engine approach.

The competing Hawker P.1154 had been cancelled in 1965 by the government just as the prototypes were under construction; however, its subsonic cousin, the Hawker-Siddeley Kestrel VTOL attack aircraft was flying in tri-partite trials with the UK, US and West Germany.

Some of the P.1154 work contributed to the final operational vertical take-off fighter based on the Kestrel, the highly successful Harrier.

[18] Akin to the earlier Balzac V testbed, the Mirage IIIV was outfitted with a total of nine engines: a single SNECMA-modified Pratt & Whitney JTF10 turbofan, designated TF104, capable of producing up to 61.8 kN (13,900 lbf) of thrust, and eight Rolls-Royce RB162-1 engines, each being capable of generating a maximum of 15.7 kN (3,525 lbf) thrust, which were mounted vertically in pairs around the centreline.

[18] A key design feature of the Mirage IIIV to improve vertical flight performance was the installation of movable thrust deflector doors ahead of the nozzles set in the aircraft's underside.

As the engines accelerated to full power, these doors would automatically drop to a 90° position in order to obtain maximum lift thrust.

[20] Throughout development, the electronics were given substantial attention; it was this element of the design that has been attributed as being a major contributing factor to the cost overruns which impacted the programme.