Overview:Eight artists are still in the competition, and this week they must conquer portraiture. To celebrate the RAF centenary the artistic travelling circus has moved to RAF Hendon. The first task our painters are confronted with are the youthful faces of two RAF cadets. Thankfully their mentors, Diana Ali and Pascal Anson, are on hand to help them with the all-important sense of proportion. If they get that wrong they will have no chance of creating a likeness. This week's masterclasses are full of helpful tips on capturing expression and new ways of mark making and blocking to improve their compositions. With the arrival of judges Lachlan Goudie and Daphne Todd comes the second challenge. This time our budding Picassos have to deal with the other end of the age spectrum. They must capture the wisdom and spirit of our two sitters, both of whom are veterans of the RAF, and who have over 180 years between them. The artists' efforts are put in front of ex-RAF personnel and members of the public, who choose their favourite to send through to next week. The rest are at the mercy of our judges, who will be dispatching someone from the competition. Overseeing proceedings, providing words of encouragement and a shoulder to cry on, as always, are Mariella Frostrup and Reverend Richard Coles.