DOUBLE DUCHESS: The Duchess of Cambridge was quietly navigating her way around London last week for the purposes of work — and play. On Wednesday, she made a private, low-key visit to an art therapy charity for children, known as The Art Room. She was dressed in jeans and a sweater for the visit to the Robert Blair Primary School in north London, which hosts a branch of the charity. The duchess has been spending the autumn months researching the charities that she may one day support. Late Friday morning, meanwhile, she was spotted shopping at L.K. Bennett near Sloane Square. A spokeswoman for the footwear and ready-to-wear brand — one of the duchess’ favorites — confirmed that she visited the store at the Duke of York Square, but declined further comment.