Thank you very much for your suggestions!
Since Friday I've eaten a banana with my breakfast everyday. And before my run this morning I did a few minutes of gentle stretching in the changing rooms.
Had a little bit of discomfort in one calf after about 8 minutes in, but it passed quite quickly and then there was no stopping me.
I stretched again at the end, and then had a high protein lunch and some milk. Feel really great!
Can't wait to do it all again tomorrow!