The Liz Carlyle series

When pirates attack a cargo ship off the Somalian coast, one of them is found to be a British-born Pakistani. MI5 Intelligence Officer Liz Carlyle is brought in to establish how and why a young British Muslim could end up onboard a pirate skiff in the Indian Ocean, armed with a Kalashnikov. After an undercover operative connected to the case turns up dead in Athens, it looks like piracy may be the least of the Service's problems...