A little while after Thomson became warehousekeeper, several of those involved in the management of the Corporation started speculating in shares on a very large scale. This seems to have begun because Grant owed money to Thomson, and both he and Burroughs had debts to Robinson from earlier stockjobbing. The partnership of five consisted of Sir Alexander Grant, William Burroughs, William Squire, George Robinson, and John Thomson. In October 1727, they began to buy the corporation's shares, this all being handled by Robinson who was a stockbroker in Exchange Alley. They then heard of lead mines in Scotland belonging to Sir Robert Sutton and others, whose sale they proposed to the York Buildings Company. They bought shares in it, and those shares rose in value.