When can I claim mileage/travelling expenses?

Relevant Travelling Expenses may only be claimed where a member of a police force is:-

1. A)

i)  required to perform his normal daily period of duty in more than one tour of duty, or

ii) recalled to duty between two tours of duty, 

and travels to and from his home between tours, or, as the case may be, in consequence of his recall (in this paragraph referred to as "relevant travelling") 

1. B)

Relevant travelling expenses shall be treated as expenses incurred in the execution of duty, and, unless they are expenses in respect of which an allowance is payable under these Regulations and determinations thereunder, the member concerned shall be reimbursed those expenses to the extent they do not exceed such reasonable limit as the chief officer of police may fix. 

Regulation 34, Annex V(5), Police Regulations and Determinations 2003