How six Vanguards could enter service before 1939

Could Britain build four to six Vanguard-type battleships while keeping the old ships available long enough to transfer their turrets?

Yes, with a settled 1934 design, paired annual orders and staged six-month turret-transfer periods.

The scheme depends on early design consensus and a steady ordering rhythm of roughly two hulls per year. Older R-class and possibly Queen Elizabeth-class ships would surrender their 15-inch turrets in carefully timed groups. That could limit the period in which the fleet is short of two ships to about six months per transfer cycle. Six fast battleships before the war would radically strengthen both the Home and Mediterranean fleets, though treaty politics would be difficult.