Late last year, during an otherwise routine speech at RUSI, Mr Wallace slipped in a comment about achieving interoperability with allies. I'd wager few present knew that if you want interoperability even between our own Services, and often within a Service, you've got to sneak it in and try to avoid the 'I' word in requirements. He was in the Army until 1998, and there's a good chance he knew that. I always wondered if that policy changed, and my first thought was 'cost'. Perhaps he's thinking about where it will come from?