Tributes have been paid from across the political spectrum after Sir Paul Grice announced that he is to stand down in September.
In a letter to MSPs he says it has been a "fantastically rewarding" two decades.
"It has been a privilege and a pleasure to have been involved with the Parliament since the beginning and to have had the opportunity to play a part in its development into a successful and well-respected institution," Sir Paul stated.
"My enthusiasm for the Parliament and commitment to what it stands for is undimmed, but now feels like the right time for me to go."
Tory Deputy leader Jackson Carlaw said: "On behalf of the Scottish Conservatives I would like to thank Sir Paul Grice for his service and wish him every happiness in his new role."