Cheers.
Encounter date was 23rd, so my weekly shopping trip. Visited 4 shops, 3 of them for less than 5 minutes.
So, Tesco, in a mask, no way was I walking around with the same person for 15 minutes!
I've been told by the app this evening to isolate for 7 days. As the isolation from contact is now 10 days I assume contact must have been on 24th.
Apart from a one hour solo run I didn't leave the house.