Thanks, it's not until October so I've got a little time
Not sure what you meant by:
It's possible to run a quickest half of under 40 miles per week, although probably not ideal. Under 20, after a few weeks, could get you round in relative comfort.
Mike.
Sorry, mobile phone autocorrect runs wild again.
I was suggesting that it's possible to run a quickish half marathon whilst training for less than 40 running miles per week (when I was a lad I was under 70 minutes on this sort of mileage), and that even if you consistently ran only 20 miles per week you would get around comfortably.
Keys are to:
1. build up slowly - running loads your body differently than the bike
2. run regularly - i'd aim to get to at least 3 times a week
3. gradually increase the distance of your weekly long run and the speed of a shorter one (when you are stronger you might add intervals of some sort)
4. enjoy it
October gives you plenty of time so you can have a lovely spring and summer heading out into the wilds where you live