What the Royal Navy meant by 70 cruisers

Did the Royal Navy's estimate of 70 cruisers mean 70 modern ships?

Not necessarily; it meant 70 cruisers capable of carrying out required modern roles, including older ships that could be converted for useful service.

The key word is capability rather than age. Older C-class cruisers and other adapted ships could still count if they performed missions required in modern war. This interpretation changes how the numerical requirement should be compared with budgets and replacement programs.