A weekend in London

After many years since my last visit, I spent a long weekend in London. Among my various impressions, I note that I didn't touch any cash whatsoever for the entire stay. Even more: if it weren't for a guy in front of me at the cash register in a pub, who was paying with a banknote, I would've not seen any cash during my visit. It's possible this way one runs the risk of overspending, but nice.