In November 2015, it was announced that he was to be the first Scottish Sheriff to be appointed a member of the Royal Household in Scotland as Falkland Pursuivant Extraordinary at the Court of the Lord Lyon.
Plean succeeded Malcolm Strang-Steel WS as Secretary to the Standing Council of Scottish Chiefs in 1984 and served until 2003, but had to stand down from this post in order to carry out his duties as Procurator Fiscal to the Lyon Court impartially.
In addition to his specialist work in peerage and heraldic law he has deep interest in judicial procedure.
He served on the Scottish Courts Rules Council and other Regulatory bodies in Scotland.
Colonel, as an external Judge Advocate in the California Army Reserve reviewing Court Martial procedures.