Just back from the Barcelona marathon.
Averaged about 27 minutes per 5k till the 30k point then my knee decided not to play anymore and I had to drop off the pace badly and stumbled across the line in 4 hours 23 minutes.
Not a disastrous time but was aiming for under 4 hours
Still I can try again in 6 weeks at London and there doesn't seem to be any lasting damage.