By all accounts the Ark Royal was years on the slip way, maybe 18 not sure, due to modifications by the MOD. Apparently as the band was approaching the shipyard, she broke free from her chocks and launched herself with a load of shipwrights beneath her.
7 years from keel laying to launch and then 5 years fitting out in the Lairds Basin. The 7 years on the slipway was mainly due to changing the Lairds workforce priorities.
After her keel was initially laid down in 1943 the workforce was continually being switched to building new Merchant Ships to replace the hammering we took in the Battle of the Atlantic.
When she eventually launched there was over 50,000 people in the crowd to cheer the launch.
The 5 years fitting out (the usual is 2 years) was due to the MOD changes, which were a new side on deck edge lift and then steam catapults were fitted.
In that same 12 year period Lairds had also built another 130 ships of various sizes, which was British Shipbuilding at it's best.
She then lost another year alongside in Gladstone Dock, when during her pre-acceptance sea trials, one of her 3 boiler turbines was stripped and wrecked which resulted in a major refit and replacement.
Her last claim to fame, before she was scrapped in 1979 after 29 years in service, was to act as the Fleet Flag Ship and lead the steam past of 61 Royal Navy warships down the English Channel, after the Silver Jubilee Spithead Review in 1977.