The New York firm led by Annabelle Selldorf will collaborate with the UK practices Purcell and Lawson Ward Studio to improve access, sustainability and visitor experience at Hertford House

As London’s National Gallery launches its “once-in-a-lifetime” rehang, Ben Luke asks: what is the right shade behind the art?

A tour of the remodelled building, five months before its reopening, shows the New York architect has created a spectacular main entrance closely integrated with the rest of the London institution and with the public space of Trafalgar Square