On 18 May 1951, the first prototype, serial number WB210 took to the air for its maiden flight, within the deadline that George Edwards had promised, only 27 months since the contract had been issued.
It was several months before a competitor, the Short Sperrin that had straight (not swept) wings and was not orderd.
 The Valiant pilot was Captain Joseph "Mutt" Summers, who had also been the original test pilot on the Supermarine Spitfire, and wanted to add another "first" to his record before he retired.
His co-pilot on the first flight was Gabe "Jock" Bryce, who succeeded Summers as Vickers' chief test pilot upon his retirement shortly afterwards.
The next month, the Vickers Type 660 was given the official name of "Valiant", recycling the name given to the Vickers Type 131 general-purpose biplane of 1931.
The name Valiant had been selected by a survey of Vickers employees.

On 11 January 1952, the first Valiant prototype was lost while making internal noise measurements for the V.1000 programme.
Testing included engine shutdowns and re-lights, one of which caused a fire in the starboard wing; most of the crew managed to escape the aircraft safely, except for the co-pilot, who struck the tail after ejecting.
 
On 11 April 1952, the second prototype WB215 made its maiden flight, after modifications to the fuel system.
 It was fitted with more powerful RA.7 Avon engines with 7,500 pounds-force (33 kN) thrust each, rather than the Sapphires that had been originally planned; it also featured more rounded air inlets, replacing the narrow slot-type intakes of the first prototype, in order to feed sufficient air to the more powerful engines.
The short delay until the second prototype became available meant that loss of the prototype did not compromise the development schedule.

The Valiant B2.
 One of the three prototypes was the B.2 version.
The B.2 was intended to serve as a Pathfinder aircraft, flying at low level to mark targets for the main bomber force.
To cope with increased air turbulence at low level, the B.2 had a strengthened airframe.
In particular, the wing was strengthened with the removal of the cut-outs in the wing structure into which the main wheels retracted, allowing the wing torsion box structure to be uninterrupted and giving more room for internal fuel storage; instead the main landing gear, which had four wheels instead of the two wheels of the B.1, retracted backwards into large fairings set into the rear of the wings.
The B.2 had a lengthened fuselage with a total length of 112 ft 9 in (34.37 m), in contrast to a length of 108 ft 3 in (32.99 m) for the Valiant B.1, with the extra length giving room for more avionics.

The prototype B.2, serial number WJ954 first flew on 4 September 1953.
Finished in a gloss black night operations paint scheme, it became known as the "Black Bomber".
Its performance at low level was superior to that of the B.1 (or any other V-bomber), particularly at sea level, with the aircraft being cleared for 580 mph (930 km/h) at low level (with speeds of up to 640 mph (1,030 km/h) being reached in testing).
This was compared to the B.1's sea-level limit of 414 mph (665 km/h).
The Air Ministry ordered 17 production B.2s, which were to be powered by Rolls-Royce Conway turbofans.
Although the Valiant B.2's low-level capabilities were significant, the programme was abandoned bacause it was considered that the World War 2 "Pathfinder concept" was obsolete in the nuclear era.
The B.2 prototype was used for tests for a few years, including testing use of rockets to boost takeoff, contributing to improvements for the Valiant B.1, before being scrapped in 1958.
On 18 May 1951, the first prototype, serial number WB210 took to the air for its maiden flight, within the deadline that George Edwards had promised, only 27 months since the contract had been issued. It was several months before a competitor, the Short Sperrin that had straight (not swept) wings and was not orderd.  The Valiant pilot was Captain Joseph "Mutt" Summers, who had also been the original test pilot on the Supermarine Spitfire, and wanted to add another "first" to his record before he retired. His co-pilot on the first flight was Gabe "Jock" Bryce, who succeeded Summers as Vickers' chief test pilot upon his retirement shortly afterwards. The next month, the Vickers Type 660 was given the official name of "Valiant", recycling the name given to the Vickers Type 131 general-purpose biplane of 1931. The name Valiant had been selected by a survey of Vickers employees.
On 11 January 1952, the first Valiant prototype was lost while making internal noise measurements for the V.1000 programme. Testing included engine shutdowns and re-lights, one of which caused a fire in the starboard wing; most of the crew managed to escape the aircraft safely, except for the co-pilot, who struck the tail after ejecting.  
On 11 April 1952, the second prototype WB215 made its maiden flight, after modifications to the fuel system.  It was fitted with more powerful RA.7 Avon engines with 7,500 pounds-force (33 kN) thrust each, rather than the Sapphires that had been originally planned; it also featured more rounded air inlets, replacing the narrow slot-type intakes of the first prototype, in order to feed sufficient air to the more powerful engines. The short delay until the second prototype became available meant that loss of the prototype did not compromise the development schedule.
The Valiant B2.  One of the three prototypes was the B.2 version. The B.2 was intended to serve as a Pathfinder aircraft, flying at low level to mark targets for the main bomber force. To cope with increased air turbulence at low level, the B.2 had a strengthened airframe. In particular, the wing was strengthened with the removal of the cut-outs in the wing structure into which the main wheels retracted, allowing the wing torsion box structure to be uninterrupted and giving more room for internal fuel storage; instead the main landing gear, which had four wheels instead of the two wheels of the B.1, retracted backwards into large fairings set into the rear of the wings. The B.2 had a lengthened fuselage with a total length of 112 ft 9 in (34.37 m), in contrast to a length of 108 ft 3 in (32.99 m) for the Valiant B.1, with the extra length giving room for more avionics.
The prototype B.2, serial number WJ954 first flew on 4 September 1953. Finished in a gloss black night operations paint scheme, it became known as the "Black Bomber". Its performance at low level was superior to that of the B.1 (or any other V-bomber), particularly at sea level, with the aircraft being cleared for 580 mph (930 km/h) at low level (with speeds of up to 640 mph (1,030 km/h) being reached in testing). This was compared to the B.1's sea-level limit of 414 mph (665 km/h). The Air Ministry ordered 17 production B.2s, which were to be powered by Rolls-Royce Conway turbofans. Although the Valiant B.2's low-level capabilities were significant, the programme was abandoned bacause it was considered that the World War 2 "Pathfinder concept" was obsolete in the nuclear era. The B.2 prototype was used for tests for a few years, including testing use of rockets to boost takeoff, contributing to improvements for the Valiant B.1, before being scrapped in 1958.
Vickers Valiant