What lessons from British rearmament before 1939 apply today?

What lessons from Britain's rearmament before the Second World War are being forgotten?

Defence choices need a wider budget context, and wartime equipment depends on preparation before war. Radar and other British capabilities had substantial prewar development behind them.

Defence spending competes with priorities across the public budget, including debt payments. Framing the choice entirely around defence versus welfare, health, and education leaves out other spending decisions. Britain's preparations for the Second World War also began well before fighting started. Radar and other wartime capabilities depended on earlier design and development, which the familiar image of emergency invention after 1939 obscures.