The supplementary vote system will be used for the mayoral election [REF].
Eligible electors are registered to vote by 13 April 2017; British, Commonwealth or European Union citizens; aged 18 or over by 4 May 2017; and resident in the seven boroughs that make up the West Midlands Combined Authority (Birmingham, Coventry Dudley, Sandwell, Solihull, Walsall, and Wolverhampton) [REF].