In the late 1950s, the British Government began the process of replacing its early second-generation jet combat aircraft in service with the Royal Air Force (RAF) and Fleet Air Arm (FAA).
At the time, the British aerospace industry was still the major provider of aircraft to the British armed forces, and designs from several companies were in service.
The 1957 Defence White Paper precipitated a significant change in the industry as the Government compelled major aerospace manufacturers to amalgamate using new aircraft contracts as an incentive.
 As a result two large groups emerged; The British Aircraft Corporation was formed by the merger of English Electric, Vickers-Armstrongs, Bristol and Hunting, and Hawker Siddeley was formed from the merger of Hawker Siddeley Aviation, Folland, de Havilland and Blackburn.

At this time, the RAF was looking to replace the English Electric Canberra light bomber in the long-range interdictor role, and the Hawker Hunter in the close air support role, while the Royal Navy sought an aircraft to assume the fleet air defence role from the de Havilland Sea Vixen.
BAC, through its English Electric subsidiary, had begun developing a new high-performance strike aircraft, the TSR-2, which was intended for long-range, low-level strike missions with conventional and tactical nuclear weapons, as well as tactical reconnaissance.
Hawker Siddeley was also developing the P.1154, a proposed supersonic version of its P.1127 V/STOL demonstrator, that could be marketed to both the RAF and Royal Navy to fulfil a number of roles: close air support, air superiority and fleet air defence.

During the early 1960s, aircraft development became increasingly expensive, resulting in major projects often becoming mired in political and economic concerns.
The development of the TSR-2 saw increasing cost overruns, combined with the presence of a potentially cheaper alternative then under development in the United States, the General Dynamics F-111.
The P.1154 was subject to the ongoing inter-service rivalry between the Royal Navy and RAF, which led to two wildly differing specifications being submitted for the aircraft that were impossible to fulfil with a single airframe.

In February 1964, the Royal Navy withdrew from the P.1154 project, and moved to procure a new fleet air defence interceptor.
It eventually selected the McDonnell F-4 Phantom, then in service with the US Navy as its primary air defence aircraft, intended to be operated from both existing and planned aircraft carriers.
This better suited the Royal Navy, as the Phantom had two engines (providing redundancy in the event of an engine failure), was cheaper than the P.1154, and was available immediately.
In October the same year, the general election brought the Labour Party back into power.
The new government undertook a defence review, which led to the publication in February 1966 of a white paper that cancelled several projects, including both the P.1154 and the TSR-2.
As a consequence, the government had to find alternatives to replace the Canberra and Hunter for the RAF, and eventually chose two types.
To replace the Canberra in the long-range role (which was intended for the TSR-2), the F-111 was selected, with plans for a redesigned variant, while the roles undertaken by the Hunter (for which P.1154 was to be procured) would be undertaken by a further purchase of F-4 Phantoms.

As the Phantom had been developed primarily for fleet air defence, the Royal Navy was happy with the choice of the aircraft as its Sea Vixen replacement, given that the type had been operational in that role with the US Navy since 1961, whilst US aircraft had successfully undertaken touch-and-go landings on both HMS Hermes and HMS Victorious.
The RAF was less enthusiastic, as the Phantom was primarily designed to operate in the air defence rather than the close air support role, and had been selected as its Hunter replacement more as a way of decreasing the per-unit cost of the overall UK order.

Partly as a means of guaranteeing employment in the British aerospace industry, agr
In the late 1950s, the British Government began the process of replacing its early second-generation jet combat aircraft in service with the Royal Air Force (RAF) and Fleet Air Arm (FAA). At the time, the British aerospace industry was still the major provider of aircraft to the British armed forces, and designs from several companies were in service. The 1957 Defence White Paper precipitated a significant change in the industry as the Government compelled major aerospace manufacturers to amalgamate using new aircraft contracts as an incentive.  As a result two large groups emerged; The British Aircraft Corporation was formed by the merger of English Electric, Vickers-Armstrongs, Bristol and Hunting, and Hawker Siddeley was formed from the merger of Hawker Siddeley Aviation, Folland, de Havilland and Blackburn.
At this time, the RAF was looking to replace the English Electric Canberra light bomber in the long-range interdictor role, and the Hawker Hunter in the close air support role, while the Royal Navy sought an aircraft to assume the fleet air defence role from the de Havilland Sea Vixen. BAC, through its English Electric subsidiary, had begun developing a new high-performance strike aircraft, the TSR-2, which was intended for long-range, low-level strike missions with conventional and tactical nuclear weapons, as well as tactical reconnaissance. Hawker Siddeley was also developing the P.1154, a proposed supersonic version of its P.1127 V/STOL demonstrator, that could be marketed to both the RAF and Royal Navy to fulfil a number of roles: close air support, air superiority and fleet air defence.
During the early 1960s, aircraft development became increasingly expensive, resulting in major projects often becoming mired in political and economic concerns. The development of the TSR-2 saw increasing cost overruns, combined with the presence of a potentially cheaper alternative then under development in the United States, the General Dynamics F-111. The P.1154 was subject to the ongoing inter-service rivalry between the Royal Navy and RAF, which led to two wildly differing specifications being submitted for the aircraft that were impossible to fulfil with a single airframe.
In February 1964, the Royal Navy withdrew from the P.1154 project, and moved to procure a new fleet air defence interceptor. It eventually selected the McDonnell F-4 Phantom, then in service with the US Navy as its primary air defence aircraft, intended to be operated from both existing and planned aircraft carriers. This better suited the Royal Navy, as the Phantom had two engines (providing redundancy in the event of an engine failure), was cheaper than the P.1154, and was available immediately. In October the same year, the general election brought the Labour Party back into power. The new government undertook a defence review, which led to the publication in February 1966 of a white paper that cancelled several projects, including both the P.1154 and the TSR-2. As a consequence, the government had to find alternatives to replace the Canberra and Hunter for the RAF, and eventually chose two types. To replace the Canberra in the long-range role (which was intended for the TSR-2), the F-111 was selected, with plans for a redesigned variant, while the roles undertaken by the Hunter (for which P.1154 was to be procured) would be undertaken by a further purchase of F-4 Phantoms. 
As the Phantom had been developed primarily for fleet air defence, the Royal Navy was happy with the choice of the aircraft as its Sea Vixen replacement, given that the type had been operational in that role with the US Navy since 1961, whilst US aircraft had successfully undertaken touch-and-go landings on both HMS Hermes and HMS Victorious. The RAF was less enthusiastic, as the Phantom was primarily designed to operate in the air defence rather than the close air support role, and had been selected as its Hunter replacement more as a way of decreasing the per-unit cost of the overall UK order.
Partly as a means of guaranteeing employment in the British aerospace industry, agr
McDonnell Douglas Phantom in UK service