My transactions are to / from Middle East and East Africa. Some banks routinely ask what the transaction is for. Your declaring 'oh, it's not money laundering' doesn't mean they'll assume it isn't. Don't forget that banks can report any transaction at all, not just international, that they deem not to conform to a customer's regular patterns. They are legally obliged to report any suspicious transactions so they report anything at all just to cover their asses - one newspaper said it could be as little as £200. Why on earth don't they concentrate on proper problems instead of micro-matters like this?

As for the question of airports, I would never, ever carry large sums of cash on my person - especially not to East Africa. One of the ground rules of travel there is dress down: this advice stretches to the wallet too - slim it down.