Valiant and her sister submarine Warspite truly moved the Royal Navy into a new era where the submarine became the capital ship of the fleet. The nuclear propulsion capability meant that these submarines could remain at sea for extended periods of time. The only limitation on these unique vessels being the twin requirements of the amount of food they could carry and the psychological effects on the ships company of long periods at sea.

These "Fleet Submarines" became the striking power of the fleet in which they served and at the same time they became the single most effective anti-submarine weapon of the day. As early as April 1967, Valiant set a new submerged record for a British submarine when she completed the 12,000 mile dived passage home from Singapore in 28 days. The Valiant class were the first all-British nuclear submarine.

After 30 years service Valiant was laid up at Devonport dockyard awaiting disposal.