Re: P1154
Contary to the last poster's statements, the P.1154 project was not called Kestrel as that was the initial name for the P.1127 prototypes ( I suspect that if P1154 had ever been constructed, it would have recieved the Harrier name).
P.1154 was designed to meet a NATO requirement for a V/Stol strike fighter (NBMR - 3), & at the time (the late 1950's), speed was considered a primary requirement.
( A previous submission, P.1150, which was capable of Mach 1.3 had been rejected, as it was considered too small to meet the requirement ).
To meet this requirement, Bristol delevoped a engine based on their Pegasus design, using Plenium Chamber Burning (PCB for short), effectively a afterburner for a vectored thrust engine.
By contrast, the French submission, for NBMR-3, the Dassault Mirage III V/Stol "Balzac" used a dedicated Rolls Royce lift engine coupled with the Mirage's existing Atar engine to meet the requirement...
P.1154 however fell foul of interservice rivalries, as the Royal Navy had a pet project it wanted funding for, namely the CVA-01 "Supercarrier" programme a/k/a the Queen Elizabeth class, which was due to enter service, in the mid 1970's as a replacement for the Ark Royal...
As a result, the Royal Navy allegedly tried to scuttle every project that competed with CV-01 for funding, including P.1154 & TSR-2...
Ironically, CV-01 was itself cancelled, as a indirect result of the U.S devaluing the Dollar in late 1967, in part to pay for the Vietnam War.
As a result of the devaluation of the dollar, the pound in turn, had to be decoupled from the Gold Standard, & massively devalued in order to prevent a balance of payments crisis, (By contrast, the U.S had decoupled the dollar from the Gold Standard in mid 1963).
As such, a austerity programme had to be initated, with regards to Government spending, & CV-01 had to go.
A attempt was made In the mid 1970's, by BAC, MacDonnell Douglas & Rolls Royce to sell the P.1150 concept to the U.S Marine Corps, under the designation AV-16...
For more information about P.1154,& TSR-2, then I would recommend reading Derek Wood's classic work on the post war British Aircraft Indrustry, Project Cancelled...