Storied Berkeley Square pied-à-terre seeks £6.5mn

Rare freehold on Craven Street, currently laid out as a one-bed, is 'a unique opportunity to create a masterpiece', say agents.

'Shell and core' unit came with an illustrious past as the former residence of Countess Raine Spencer.

1901 specimen is regarded as one of the finest works by the architect George Walton.