11.  An employer of a mobile worker shall

(a) request from each mobile worker details of any time worked by that worker for another employer;

(b) include time worked for another employer in the calculation of the mobile worker's working time;

(c) keep records which are adequate to show whether the requirements of these Regulations are being complied with in the case of each mobile worker employed by him to whom they apply;

(d) retain such records for at least two years after the end of the period covered by those records;

(e) provide, at the request of a mobile worker, a copy of the record of hours worked by that worker;

(f) provide to an enforcement officer copies of such records relating to mobile workers as the officer may require;

(g) provide to a mobile worker or enforcement officer copies of such documentary evidence in the employer's possession as may be requested by the worker or officer in relation to records provided to him in accordance with paragraph (e) or (f) above.