I had a very embarrassing incident at Carrefour on Saturday when my card was refused for €60 of groceries and I had no other method of payment - even the ATM spat it back at me.
Called Barclays this morning to find out why - when my account was in healthy credit - the card was being refused.
Barclays informed me that multiple payments on the card overseas triggered a security safeguard and the card had been stopped.
I would call this a remarkably proactive move on the bank's behalf. Except I haven't lived in the UK for the last four years.