The first squadron to be equipped with the Valiant was 138 Squadron, which formed at RAF Gaydon on 1 January 1955, with 232 Operational Conversion Unit forming at Gaydon on 21 February 1955 to convert crews to the new bomber.
Since the Valiant was part of an entirely new class of bombers for the RAF, the crews for the new type were selected from experienced aircrew, with first pilots requiring 1,750 flying hours as an aircraft captain, with at least one tour flying the Canberra, with second pilots needing 700 hours in command and the remaining three crewmembers had to be recommended for posting to the Valiant by their commanding officers.
Valiants were originally assigned to the strategic nuclear bombing role, as were the Vulcan and Victor B.1s when they became operational.
At its peak, the Valiant equipped ten RAF squadrons.

According to Gunston and Gilchrist, the Valiant had performed "extremely well" during the annual bombing competition hosted by American Strategic Air Command (SAC).
American interest in the Valiant resulted in a visit to Vickers by USAF generals Vandenberg, Johnson and LeMay.
Vickers test-pilot Brian Trubshaw believed that George Edwards was put under some pressure to build the Boeing B-47 under license.
The only result from the visit was Le May's insistence that the Valiant pilot side-by-side seating be incorporated in the B-52 instead of the tandem arrangement in the B-47 and prototype B-52.

On 11 October 1956, a Valiant B.1 (WZ366) of No 49 Squadron was the first RAF aircraft to drop a British atomic bomb when it performed a test drop of a down-rated Blue Danube weapon on Maralinga, South Australia.
Windscreen blinds were fitted in advance of the test to protect the crew from the intense flash of light from the nuclear detonation.
Following the landing of the aircraft after deploying the weapon, WZ366 was assessed for potential damage and for radioactive contamination.

On 15 May 1957, a Valiant B(K).1 (XD818) dropped the first British hydrogen bomb, the Short Granite, over the Pacific as part of Operation Grapple.
No 49 Squadron was selected to perform the live weapon drop, and were equipped with specially-modified Valiants to conform with the scientific requirements of the tests and other precautionary measures to protect against heat and radiation.
However, the measured yield was less than a third of the maximum expected although achieving a thermonuclear explosion.

On 8 November 1957 a British hydrogen bomb detonated with its planned yield in the Grapple X test.
The Grapple series of tests continued into 1958, and in April 1958 the Grapple Y bomb exploded with ten times the yield of the original "Short Granite".
Testing was finally terminated in November 1958, when the British government decided it would perform no more air-delivered nuclear tests.

Originally the bombing role was to have been carried out at high altitude, but following the shooting down in 1960 of the Lockheed U-2 flown by Gary Powers by an early Soviet SA-2 Guideline missile, the SAM threat caused bomber squadrons to train for low-level attack as a means of avoiding radar detection when flying within hostile airspace.
They were repainted in grey/green camouflage with normal markings, replacing their anti-flash white scheme.
By 1963, four Valiant squadrons (49, 148, 207 and 214) had been assigned to SACEUR in the low-level tactical bombing role.
By this point, there had been a noticeable decline in flying rates for the type.
The first squadron to be equipped with the Valiant was 138 Squadron, which formed at RAF Gaydon on 1 January 1955, with 232 Operational Conversion Unit forming at Gaydon on 21 February 1955 to convert crews to the new bomber. Since the Valiant was part of an entirely new class of bombers for the RAF, the crews for the new type were selected from experienced aircrew, with first pilots requiring 1,750 flying hours as an aircraft captain, with at least one tour flying the Canberra, with second pilots needing 700 hours in command and the remaining three crewmembers had to be recommended for posting to the Valiant by their commanding officers. Valiants were originally assigned to the strategic nuclear bombing role, as were the Vulcan and Victor B.1s when they became operational. At its peak, the Valiant equipped ten RAF squadrons.
According to Gunston and Gilchrist, the Valiant had performed "extremely well" during the annual bombing competition hosted by American Strategic Air Command (SAC). American interest in the Valiant resulted in a visit to Vickers by USAF generals Vandenberg, Johnson and LeMay. Vickers test-pilot Brian Trubshaw believed that George Edwards was put under some pressure to build the Boeing B-47 under license. The only result from the visit was Le May's insistence that the Valiant pilot side-by-side seating be incorporated in the B-52 instead of the tandem arrangement in the B-47 and prototype B-52.
On 11 October 1956, a Valiant B.1 (WZ366) of No 49 Squadron was the first RAF aircraft to drop a British atomic bomb when it performed a test drop of a down-rated Blue Danube weapon on Maralinga, South Australia. Windscreen blinds were fitted in advance of the test to protect the crew from the intense flash of light from the nuclear detonation. Following the landing of the aircraft after deploying the weapon, WZ366 was assessed for potential damage and for radioactive contamination.
On 15 May 1957, a Valiant B(K).1 (XD818) dropped the first British hydrogen bomb, the Short Granite, over the Pacific as part of Operation Grapple. No 49 Squadron was selected to perform the live weapon drop, and were equipped with specially-modified Valiants to conform with the scientific requirements of the tests and other precautionary measures to protect against heat and radiation. However, the measured yield was less than a third of the maximum expected although achieving a thermonuclear explosion. 
On 8 November 1957 a British hydrogen bomb detonated with its planned yield in the Grapple X test. The Grapple series of tests continued into 1958, and in April 1958 the Grapple Y bomb exploded with ten times the yield of the original "Short Granite". Testing was finally terminated in November 1958, when the British government decided it would perform no more air-delivered nuclear tests.
Originally the bombing role was to have been carried out at high altitude, but following the shooting down in 1960 of the Lockheed U-2 flown by Gary Powers by an early Soviet SA-2 Guideline missile, the SAM threat caused bomber squadrons to train for low-level attack as a means of avoiding radar detection when flying within hostile airspace. They were repainted in grey/green camouflage with normal markings, replacing their anti-flash white scheme. By 1963, four Valiant squadrons (49, 148, 207 and 214) had been assigned to SACEUR in the low-level tactical bombing role. By this point, there had been a noticeable decline in flying rates for the type.
Vickers Valiant