"17. The hours of employment are forty hours per week. The employee will be issued with a shift pattern on the completion of training. This shift pattern is subject to change by the Company in line with operational requirements at any time during the period of employment. 18. ........... 19. The employee will work reasonable overtime when required. While every effort will be made to give reasonable notice of overtime, no minimum period of notice is guaranteed to provide overtime working. 20. Two meal breaks will be provided during the course of any 12 hour shift. Whilst the Company will offer as much flexibility with regard to meal breaks as possible, any employee not offered a meal break to commence between 1200 hours-1500 hours will be paid an half hour overtime in lieu of the meal break not being offered"