The Great Interior Design Challenge

In the third and final round of this heat, two designers have proved their talent, but now only one can win a place in the quarter-final. The backdrop for this design showdown is an 18th-century Scottish castle, now converted into apartments. Once again they have just £1000, three days and a small team to make their transformations.

Our two designers are following very different briefs in two different reception rooms. One designer has been asked for an elegant lounge and dining room, and has some brilliant ideas for creating sumptuous details on a budget - but with major concerns over their choice of mirrored wall panels, the overall look may fail. Meanwhile, the other designer wrangles to give their high-ceilinged, plain sitting room a steam punk influence. However, running out of wallpaper and struggling with intricate details could threaten the entire project.

Presenter and architectural historian Tom Dyckhoff discovers more about the history of this mysterious castle, built as a fortress-like folly where things aren't quite what they seem. It is down to the judges to decide which designer has displayed enough skill and talent to go through to the quarter-final.