Checking a claim about British defence spending

Was Britain spending about half of its GDP on defence in 1938?

No. A historical-statistics table gives 259 million for public administration and defence against GDP of 4,932 million, far below 50 percent.

The claim is checked against a compiled British historical-statistics source rather than accepted from chat. The table gives a 1938 GDP figure of 4,932 million and a public-administration-and-defence figure of 259 million. Even allowing for the category wording, those numbers are nowhere near half of national output. The correction matters because claims about unlimited prewar resources can make difficult gun-development choices look artificially easy.