The pair set up a new vehicle called Millicent Holdings, which will pay £2.4m for the two companies that formed part of Stanley Gibbons' interiors division.
The deal does not include the Mallett inventory, the rental income from the former Mallett New York premises, the Bloomsbury auction and retail business and its interests in Masterpiece London.
Law is an ex-Dreweatts employee and is now the owner of London dealership Albert Amor. In 2005 he acquired the long-standing firm Partridge Fine Art with the backing of the backing of a consortium including former Culture Secretary David Mellor, although the business closed after it went into administration in 2009.
For more on this story, see next week's ATG print edition.