Tony Blair last night suffered the biggest backbench rebellion on a domestic issue of his decade in power. But the political impact of the re-volt was always destined to be more muted than his op-ponents might have wished.

Some will see the Trident rebellion as a sign of how fractious and rebellious the parliamentary party could now become under Gordon Brown, his near-certain successor - and that Labour risks moving leftwards. But more sober analysts regard last night's events as a very particular rebellion on a very particular issue.