MARY BEARD'S ULTIMATE ROME: EMPIRE WITHOUT LIMIT BBC2, 9pm Mary Beard is an expert on the Romans, but it seems that there's one question that's still puzzling her - why them? More specifically, what was it about the Romans that enabled them to build such a huge empire, and why does their legacy still seem so relevant today? It's the puzzle at the heart of this new series, which also explores some of the contradictions within the civilization.
MASTERCHEF BBC1, 9pm It's the semi-finals, which calls for a huge challenge - and the remaining eight contestants are about to face their toughest task to date. They are heading to the biggest naval base in Western Europe, ready to serve lunch to members of the Royal Navy on board the anti-submarine frigate HMS Northumberland. 24 HOURS IN POLICE CUSTODY Channel 4, 9pm Cameras follows officers from Bedfordshire Police as they race against time to investigate potential sex offenders and gather enough evidence to try to build a case. The suspects are brought to the attention of the police by the work of modern-day vigilantes. After filming their public confrontations, the paedophile hunters post the evidence on the internet, as well as demanding that the men they entrap hand themselves in to the police.
CARAVANNER OF THE YEAR BBC2, 8pm The three remaining couples work on their winning strategies as they battle it out to become Caravanner of the Year. In the final of the competition, the contestants must negotiate a demanding navigation test, and to add to the pressure, their driving skills are under scrutiny. However, the road restrictions and ban on Sat Navs quickly take their toll. Next, the camping enthusiasts take on the hospitality challenge.