Former City player Theobald, who was joint-manager with Nightingale at Ryman League Soham Town Rangers, is the new head coach at the Lilywhites.
Theobald, who made more than 200 appearances for City, guided the Ryman North club to victory at the weekend before standing down on Monday to team up again with Nightingale who got off to a winning start on Saturday with a 1-0 win over Merthyr, the club's first victory in 15 games.
Theobald said: “I am thrilled to be returning to City. It’s a great club and I am looking forward to the opportunity of working with both Robbie Nightingale and Neil Midgley and I feel we can all work well together.
“I know most of the squad and I am looking forward to getting started. Robbie got the team off to a great start but it is still a challenge to stay in the league but the win at the weekend has given everyone confidence for the weeks and months ahead.”
Nightingale said: “I am delighted that Dave has accepted the opportunity to be part of the management team at City. He has a great knowledge of the game and together with Neil Midgley will assist me with first team affairs both on the training ground and on match days.”
Nightingale was unveiled last Thursday as the successor to Dan Gleeson following his departure 24 hours earlier. Nightingale is no stranger to the Lilywhites having made over 350 appearances for the club in two spells and captaining the side that played in the last first team game at Milton Road in April 2013.
Follow the EVO-STIK League Southern on Twitter at @SouthernLeague1
Keep up-to-date with our exclusive email newsletters.
Subscribe