The 22-year-old was told he would not be offered a new deal with Mark Yates' men but was invited back in July for pre-season as he looks to return to full fitness after a foot injury.
But after 10 starts and three substitute appearances over two seasons the former Shrewsbury man will play for Terry Butcher next season in the Scottish Premier League.
"We would like to thank Harry for all his efforts during the past two seasons and we wish him all the best with his new club," a club statement said.
- Sports & Recreation
- Mark Yates