The official UK Government website explains that "The Laureateship was a lifetime appointment until 1999. Following the death of Ted Hughes, it was decided that the appointment should be for a fixed term of ten years, to give more poets the opportunity to serve."
My understanding is that on being appointed to succeed Hughes, Andrew Motion was only prepared to accept the appointment for a ten–year term. It would appear that the decision was taken at that time to make this a permanent arrangement.
An advisory panel was set up in 2018 to offer its suggestions on the scope and purpose of the next Poet Laureate, and make a recommendation to Her Majesty The Queen. The panel includes the founder of the Bradford Literature Festival and the organiser of a showcase event with the Jamaican Poet Laureate, and representatives from the British Council, Arts Council England and Arts Council Northern Ireland, Royal Society of Literature, Scottish Poetry Library, Literature Wales, The Poetry Society, Forward Arts Foundation, British Library and Poetry Book Society.
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