There's little overall tension, and the time-travelling historians come over as both panicky and amateurish – an undesirable combination, one might think, where timelines are lying about ready to be mucked up. The result is a mildly interesting 200-page novel about the ordinary heroism of British civilians during the war, bloated to 800 pages via an egregiously handled time-travel conceit, eked out with great jellied quantities of historical research, endless meandering conversations, long passages disposed into that tiresome typographical convention by which characters' inmost thoughts are spelled out in italics, and a string of inconsequential chapter-end cliffhangers/immediate resolutions that got increasingly on my nerves as the book went on. But nevertheless Eileen, Mike and Polly become increasingly anxious that the timelines are being perverted.

Since scores of historians have already gone back to such big events as the battle of Marathon and the French revolution without causing any upset, the official belief is that nothing they might do can change anything. The backstory threads are very easily picked up: 21st-century historians Eileen Ward (real name Merope), Mike Davies and Polly Churchill, having been inserted into wartime Britain, are struggling to locate the 'drops' that will get them home, all the time worried that their actions might be altering the time-lines and changing the course of the war. Readers considering buying All Clear may wonder whether they can do so without first reading Blackout. Living as we now do in the age of Kindle makes this excuse, it seems to me, rather harder to justify than might otherwise be the case. But we were told that Blackout and All Clear aren't two novels, but one novel chainsawed down the middle to accommodate the exigencies of commercial publishing.

Some grumbled that giving the 'best novel' prize to two books wasn't fair. The joint winners were Connie Willis's Blackout and Connie Willis's All Clear – the two halves of a lengthy narrative about time-travelling historians from 2060 in London during the second world war. T his year Connie Willis shared SF's blue riband prize, the Hugo, with herself.

All Clear by Connie Willis