It may have been the former home to the London College of Music, but the 310-year-old building on Great Marlborough Street now whistles its own tune in its latest incarnation as the restaurant Sucre. The sumptuous restaurant and bar is the concoction of the revered Argentine chef Fernando Trocca and award-winning bartender Renato “Tato” Giovannoni, who exported Sucre — and its accompanying bar