Grimes obtained leave of absence and went to England in August 1803. It was nearly three years before he was back in Sydney. In March 1807 he was sent to Port Dalrymple, and using the advice of Thomas Laycock, who a month earlier had become the first European to traverse the interior of Tasmania, Grimes made a survey of the district and examined the route to Hobart. Much of the route he surveyed became the Hobart Road, and many sections of the original 1808 road still form part of the Midland Highway.