Britain's Most Expensive Houses is back with a new series, as we take an exclusive peak into the country's most extraordinary properties with eye-watering price tags. From London's most coveted postcodes to grand country estates and coastal retreats, we delve into the pockets of the uber-wealthy and follow brokers as they manage multi-million-pound deals. In this first episode, top broker Josh Marks has secured the most expensive property on the open market in Britain: an £80 million penthouse in Knightsbridge. But with only six months exclusivity and a tiny pool of potential buyers, he needs to dig deep into his elite network to close a deal. In Cornwall, Ian Lillicrap is showcasing two prime properties: a £4 million coastal home with stunning views over St Ives Bay and a £1.85 million Californian-inspired retreat. Can he impress buying agent Clary Coode and achieve a double deal? And agent Tim Phillips is bringing Lynford Hall, a 20-acre country estate built in 1856 in Norfolk, to market. It's being positioned as a commercial or residential opportunity, but can Tim find someone with deep enough pockets to take on this unique estate?

Raj Gill, managing director of Knightsbridge Prime Properties, is under pressure to sell a recently renovated £18 million townhouse near Harrods while managing its lucrative rental income of £27,000 per week. In Buckinghamshire, Fine & Country agent Haydn offers an indecisive client the choice of a wing of a listed mansion, a converted farmhouse and a seven-bedroom rectory. In Stratford-upon-Avon, agent Jonathan Handsford prepares to list Birgan Lodge, a new three-storey home with a private jetty onto the Avon river.