What do historians from 2060 think they are doing messing about with the space-time continuum? Did they never watch Dr. Who? They could alter the course of the 2nd World War; create a discrepancy in the historical record - and who knows what will happen? Certainly not Polly, Michael, and Eileen. Not to mention Colin and the Hodbin children who save the day - and all without a sonic screwdriver.
Like Polly, Mike thought. It must have been hell for her when she realised her drop wouldn't open, and worse keeping it to herself these last weeks while he and Eileen talked about options she knew wouldn't work. But the worst must have been not being able to do anything about it. Lying there in the hospital worrying about what had happened to the retrieval team and whether he had messed things up by saving Hardy had been bad enough. He couldn't imagine what it would have been like if he'd already been to Pearl Harbor, even if it was a year from now, or like the day the V-1s started, three and a half years off. It didn't matter when it was. It was still heading straight at you.