Tory MP Nadhim Zahawi of Stratford-Upon-Avon presents a video about the work and there's some contextual text:
"The oil painting was commissioned in 1907 and was completed by Henry Payne in 1910. It illustrates the Plucking of the Red and White Roses in the Old Temple Gardens. Richard Plantagenet, the Duke of York, plucks a white rose signifying the House of York and his claim upon the throne. His great rival, the Duke of Somerset, John Beaufort, plucks a red rose symbolising the House of Lancaster. They invite their fellow noblemen to make a choice as to whether they pluck a red rose or a white rose."