Sitting in a terrace bar in Barcelona at the weekend, I overheard the conversation amongst two English couples at an adjacent table, as they sorted through several piles of Euro bank notes.

It went something like this :

"These are the ones wot Fred brought back from France last year, so these must be the Spanish ones .... "

I wasn't quite sure what was coming but I had an uneasy feeling that I knew where the conversation was going, and the next words confirmed my worst fears :

"So you can't use the French ones in Spain?"

The waiter was called over and beers ordered. No attempt to speak Spanish was made, but the waiter spoke sufficient English to take the order and deal with the next question as a 20 Euro note was thrust into his face :

" 'ere mate, 'ow much is this worf in our money?"

With a mixture of typical Spanish grace and gentle Catalan sarcasm, he replied : "I do not know which is your country, so it is impossible that I answer the question."

They explained to him, as if he were the one short of brain cells, that they were from England, you know .... E- N- G- L- A- N-D and he promptly replied that 20 Euros was worth about £15, not bad for a quick calculation. He went off to get the order, and the conversation continued :

"They all look the same. 'ow do you know which country they come from? What a stupid system. I mean at least wiv the coins they have sort of like, you know, different patterns, but these notes, stupid innit? Bloody 'ell."

Cringing with shame at the ignorance of fellow Anglophones, I was glad to be able to speak Spanish and as the waiter came over I told him what was going on and we hatched an evil little scheme. When they offered him a 20 Euro note to pay their bill, he looked at it, turned it over, and handed it back to them and told them it was not valid in Spain. They offered him the next one which he glanced at and accepted.

I leaned across and told them that only the German and Swiss Euro notes were valid in all of Europe, with the Greek and Portuguese ones only valid in their own countries of issue. Then they asked me how you knew where they came from.

I told them that any that had more than one 7 in the serial number were Greek, those that had more than one 6 were Portuguese, and that only ones with a 0 were valid anywhere but I wasn't too sure about the rest.

As I left they were carefully sorting through the notes, putting some aside as invalid. I spent the rest of the weekend hoping I wouldn't bump into them again, but fairly smug in the knowledge that they were unlikely to have worked out that they'd been deceived. I also wonder if they tried to find Swiss Euro coins!

P.S. There is actually a country code on each note, it is the letter preceding the serial number, for example V is Spain, U is France, S is Italy, and oddly enough J is reserved for the UK in the event that the UK should join the Eurozone - hopefully never but that's another debate.