He likes that customers their are more "talkative" than at other supermarkets and that they're rarely located next to bingo halls, possibly.
The PM said: "I find if I shop in Waitrose in Witney it takes me about twice as long, because everyone wants to stop you and have a chat, whereas in other supermarkets I find I can dart round very quickly."
You'll actually find this is due to there not being any cameras around, because as these snaps show, when the media is looking a politician will do anything to hang around and be seen in any shopping establishment...