It was pretty crowded, and I worked out that I'd have to tell one of the bar staff what I was doing, and give them £4 for someone's drink, then give them the nod when someone suitable went to the bar. It was impossible though, partly because the bar was really crowded, and partly because hardly anyone came in on their own.
Next try was in Witney on a Saturday morning when I had a bit of time, at Church Green Cafe, chosen because it's a rare place where you pay after you order.
By Tuesday I'd already opened the next challenge, and had to take action. I remembered there's a chap who goes to the Blue Boar ...
... every day for coffee, who I've met but who won't remember me. He's a good-hearted, gentle kind of bloke (can't name him because people will know him), so I got one in for him even though he wasn't there. So I sort of fulfilled the challenge.