Where an employer accepts an employee's application to change from full-time to part-time work must it permit a change back to full-time work if the employee later requests this?

Any change to the terms and conditions of an employee's contract requires the agreement of both the employee and the employer; neither party has the right to impose unilateral changes to the terms of the contract on the other party. An agreement for an employee to move from full-time to part-time work will be a mutually agreed variation to the terms of the employee's contract, which, unless expressly agreed otherwise, will be a permanent change. Any subsequent variation, for example a change back to full-time work, will similarly require agreement by both parties. There is no statutory right for an employee to insist on reverting to full-time work at a future time.