Did the physio sugest rebuilding that quickly? I ask because I had a grade 1 calf tear a couple of years ago and I know that it took me 3 weeks from the injury to running a half marathon at marathon pace, and that I wasn't running at all for at least a week after the initial injury. My physio didn't actually advise doing the half marathon because the risk of a re-tear was too high, so we agreed that I would do the race at my own risk. I did manage to do my marathon but that was (I think) 9 weeks post-injury and I did a hell of a lot of cross-training and strengthening work. Also, I think I probably got away with it because I was training for something like my 8th or 9th marathon and typically do 60-70 miles a week, so a marathon isn't quite the same ask for my body now as it was when I did my first marathon (they still hurt - a lot - but my body is much more conditioned than it used to be).
Plus, I say I got away with it, but I re-tore the same calf 6 weeks after the marathon...
DanA: I've never favoured the one single target approach, and so it is fair to say that my targets are: A: 2.45 B: 2.46.30 C: 2.48
My thinking is that C should be fine, and is as close to in the bag as anything ever is in this game, B is probable and A is possible.
I know my training has gone well, even if Bristol didn't go to plan (mostly a stress/fuelling issue, so easily explained). My view was that Cardiff was too close to the big day to race flat out (bearing in mind P&D suggest not racing more than 10 miles flat out when in marathon training), so it was a comfortably hard run, and my legs felt pretty ok on my recovery run this morning. It also fell at the end of a 68M week (peak is 70), with 14M on the Thursday and 10M on the Saturday, so was on tired legs. 3 weeks out from London (2.49) I did the Maidenhead Easter 10 @ 6.17s. Runningforfitness's race calculator reckons yeserday's 13.1 @ 6.18s was equivalent to 10 @ 6.12s, so an improvement of 5s/mile (2m 11s over the full distance) - hence I'm pretty sure about the B target.
I know that the A target will require the sort of good conditions we had yesterday/in London, but I also know that it will mean listening to my body. I had to do that at Frankfurt in 2013 when 2.57 pace just didn't feel right, and I'll do it at Frankfurt 2015 if I have to. I'd rather get 2.46.30 or 2.48 from an even paced race and finish knowing there is more to come than crash and burn.