In late March 2019 a team from Capita Real Estate and Infrastructure attempted the Welsh Three Peaks challenge. https://www.capitaproperty.co.uk/insight/news/2019/welsh-three-peaks-challenge/
17 hours and 0 minutes
The Welsh Three Peaks Challenge involves climbing Snowdon, Cadair Idris and Pen y Fan in the same day, either over 24 or 12 hours.