Prime Minister Scott Morrison has received an unwanted spanner in the works ahead of Tuesday’s return of parliament with barrister Keith Wolahan’s win this afternoon in the preselection for the safe Victorian seat of Menzies.

Wolahan, a Cambridge graduate who saw service with the ADF in Afghanistan as a special forces officer, defeated Kevin Andrews, who has held the seat since replacing our very own Neil Brown in a by-election back in May 1991.

His win has huge significance within the Victorian Liberals. It is the first time since a young and thrusting Peter Costello and David Kemp challenged sitting wets back in 1990 that federal incumbents from the state have lost their seats at preselections. It has potential to further destabilise the already-troubled state party, struggling despite the disastrous decisions of Daniel Andrews.

Its echos will also be felt in Canberra.

Labor has been the divided party with a threatened leader forced to reshuffle the ranks.

Wolahan’s win is no disaster for Scott Morrison, but it takes a few chips off the Prime Minister’s duco as parliament returns.

The defeat of the 30-year parliamentary veteran Andrews — a member of both the Howard and Abbott cabinets — is a significant event.

Its consequences detract just that bit from government unity and will be used by Labor to question the judgement of both Morrison and Treasurer Josh Frydenberg, who publicly backed Andrews (Frydenberg attended and voted in the preselection as Victoria’s most senior federal Liberal MP, a task the more prudent might have given to a proxy).

It’s a minor distraction, but still unwanted.

It also raises questions about the parliamentary ambitions of Peta Credlin.

There has long been talk that Andrews was simply seeking another term to keep the safe seat warm for her — but Credlin is more than capable of speaking for herself.