The Kent-based firm had been the demolition contractor for the Warwick Quadrant mixed-use supermarket and hotel scheme and has now signed the main contract to restart work.
Over the past week, survey work has been carried out on site, allowing RG Group to finalise its construction programme.
The scheme, which is being backed Aviva, will see the supermarket chain build a new store three times bigger than the current building.
Above the store will be extensive car parking on two levels, with a 98-bedroom hotel above that in a new five storey building. The whole project is expected to cost around £20m to build.