When I take the promotion exam is this a working day?
The short answer is yes, but see below for a fuller description.

There's nothing written down specifically in circulars on this, either PNB or HOC (except for reference to code of conduct in HOC 03/2002 - entitled 'Changes to the Police Promotion Examination'). There is a clearer reference in para 14 of annex C to a PPEB (Police promotions Examination Board) Report on the Examination Process prior to that circular which speaks of the candidate being on duty during the examination process. Clarification has been sought from the NPIA (October 2009) and it is their understanding that both examinations (I & II) are duty days and the officer is entitled to it. Dates are notified well in advance (to Chief Constables and candidates) to allow for re rostering of rest days if necessary. Officers also have to be fit and if on sick leave must provide evidence from the Force Medical Officer that they are fit enough for the exams or assessments.

From Annex C to PPEB Report 2001:
14. On the part of candidates, candidates are deemed to be on duty during their examination and are governed by the Police Code of Conduct. Unacceptable language, behaviour or attitudes will be penalised in Part II of the examination. Unacceptable language or behaviour are defined as 'any language or behaviour which falls short of the standards expected of a police officer' under the Code of Conduct in Schedule I to the Police Conduct Regulations. The Respect for Diversity competency area, which will be measured in each exercise in Part II from 1st January 2002, will be used as a basis for recording and evaluating unacceptable language and behaviour. Any candidate who scores a D in Respect for Diversity may fail the examination irrespective of what grades he or she achieves in the other competency areas. The information associated with candidates who display unacceptable language or behaviour may be forwarded to the candidate and their Chief Officer to enable candidates to receive appropriate development in these areas.
Category: GENERAL, [37]