Each force has between one and five assistant chief constables.

Assistant chief constables usually hold portfolios (e.g. for crime, operations or territorial policing).

Mr Wilmot's six assistant chief constables are likely to join the boycott in November.

The new single police service for Scotland, Police Scotland, will have six assistant chief constables.

Police authorities were empowered to choose chief constables, deputy and assistant chief constables from a Home Office shortlist.

Miss Halford, 51, one of only four women assistant chief constables, was suspended on full pay in December, 1990, over allegations of neglect of duty, discreditable conduct and falsehood.

The chief constable is assisted by a deputy chief constable (DCC) and one or more assistant chief constables (ACC).