The Helly Nahmad Gallery has signed a 15-year lease to pay £185 per sq ft across 2,959 sq ft on the sixth floor of 8 St James's Square, industry magazine Property Week reported - the highest rent ever paid for an office in the UK.
Mike Tapp, director at Green Property - the building's developer - described it as "the most prestigious office development in the world today".
"This is reflected not only in the calibre of tenant we are attracting but also the strong rents we are achieving," he told Property Week.
A report out earlier this year by Cushman & Wakefield showed London's West End is the most expensive place in the world, with an average rent of €2,344 (£1,443) per sq m per year. The next most expensive place was Hong Kong's CBD, at €1,636, followed by Midtown in New York.
This time last year, a report by CBRE - which, along with Knight Frank, advised Green Property on the St James's Square deal - showed the amount of office space under offer had increased 84 per cent on the previous quarter to its highest level since 2000.
Pilcher Hershman advised Helly Nahmad.