It's Christmas and new team member Corporal House is thrown in at the deep end.

Nick regrets showing off to his new number 2, Towerblock. Simon and Bird come to blows.

A blast from the past knocks Nick off his game. Bird tries to teach Mary a lesson.

Nick and the Lt Colonel find themselves in a battle of wills. Rocket gets a pet rat.

The team gets a visit from a government minister, to whom Mary unexpectedly takes a shine.

Bird hatches a plan to stop Nick and Mary going on about each other once and for all.

Simon's lack of trust in Mac and Rocket comes back to bite him.

We rejoin the Bluestone 42 team after the IED explosion has hit their mastiff.

The team are called out to a major operation, where events take a worrying turn.

Towerblock is put through his paces after challenging Rocket to a battle of the fittest.

The team suffer a Taliban attack, which distracts Ellen and Bird from their bickering.

Ellen has to learn to bend the rules, while Mac and Rocket do gladiatorial combat.

As the team prepare to leave Afghanistan for good, Simon receives some devastating news.