I went today with a group of patrons to Alderbrook Park in Surrey to see the Ai Weiwei pavilion which was originally designed as one of the Serpentine pavilions jointly with Herzog and de Meuron.   Alderbrook is in deepest Surrey, in that area of the North Downs beloved of late nineteenth-century industrialists where Norman Shaw built a characteristically large, tile-hung, Tudor-style house for Pandeli Talli, a Greek merchant banker, MP and bachelor.   It was bought by Albert van den Bergh, who had a margarine fortune, in 1936 and was demolished by his grandson in the late 1960s.   The pavilion, largely made of cork, is buried half underground on the slope of the Downs.