Just off the lobby at Dutch bank ING's London office on Moorgate is an unremarkable door. It is easy to miss; it looks identical to the surrounding wall panels, other than its handle. Behind it is another door, with a sign warning that the room ahead has a reduced oxygen supply and that visitors must leave immediately if an alarm sounds. Inside lies the legacy of one of the world's oldest merchant banks.  

Welcome to the clandestine Baring Archive, a collection of centuries-old documents and materials charting the story of the bank that started life on Christmas Day, 1762, as John and Francis Baring & Co. When ING acquired Barings Bank for £1 in 1995, after it was brought down by losses linked to rogue trader Nick Leeson, it acquired not just the bank's business but also the documents that detail its 230-year history.