Prince Edward - Mystery Medal

Following on the post Royals in Medals #1: The Earl and Countess of Wessex I've noticed this photo of the Wessexes at the 2011 royal wedding in Monaco.

What is the last medal Edward is wearing on his rack?  Given the occasion and the fact that it seems to have Prince Albert's cypher on the ribbon, I suppose it's something to do with Monaco, but can anyone identify it?  Thanks.

He doesn't appear to have worn it since, so it seems to have approval for local wear only.

For those interested, Edward is wearing the uniform of Commodore-in-Chief of the Royal Fleet Auxiliary.  The cypher on his should-boards and the aiguillettes reflect his appointment as an ADC to the Queen