Senior public servant Rod Hook has been axed by Premier Jay Weatherill, in a move which precedes major changes in the transport, infrastructure and urban development portfolios.

Hook, the chief executive of the Department of Planning, Transport and Infrastructure, has been the state’s most prominent public servant during Labor’s long rule since 2002.

Renewal SA chief Fred Hansen – a former thinker-in-residence – has resigned, with the government expected to make significant changes to the organisation, which was at the heart of controversy over the sale of land at Gillman.

Hook’s tenure was ended with one day’s notice, but he will receive a substantial payout.

Weatherill said Hook’s axing and Hansen’s resignation were part of a process of “renewal in the leadership of the South Australian public service”.

“This renewal should not be taken as anything other than the need to take a further step in the economic development of South Australia,” he said.

He praised both of them as “outstanding public servants” and thanked Hook for his role in an “extraordinary period of achievement”.

“I want to thank both of these men for their service and wish them all the best for the future,” he said.

Weatherill said the new leaders of the agencies would be “my picks, there’s no doubt about that”.

He said Hook was on leave after today, and would officially finish his tenure in July, with deputy chief executive John Hanlon appointed as acting chief executive.

Weatherill said he couldn’t recall having a disagreement with Hook.

Hook was the face of Adelaide’s massive infrastructure build, including the new Adelaide Oval and footbridge, the duplication of the Southern Expressway, and the electrification of the rail system.

Rare for senior public servants, the stoic media performer was often happy to take the heat on contentious issues in place of the relevant minister.

Hook’s journalist son Ben last night took to Twitter, in a post which appears to reference his father’s axing: “Sometimes I wonder why our state’s leadership struggles so much. Today I understand more clearly. Remember this date.”

Opposition Leader Steven Marshall said the decision to axe Hook had surprised him.

“It’s a bombshell,” he said.

“Rod Hook has been a faithful servant to South Australians for decades.

“He took a lot of the flack for government.

“He often made a dysfunctional government look almost competent.”

Marshall told FIVEaa’s Leon Byner that speculation Hook had become “too close” to a possible Marshall Government was misplaced.

“I think I’ve only spoken to Rod Hook once and that was when we were at the same function.

“I’ve had no personal relationship with him whatsoever.

“I’m at a complete loss as to why this would happen.”

Sources close to Hook said he was disappointed he had not been able to have a transition period to hand over to a new chief executive and wrap up his involvement with key infrastructure projects.

Labor sources had expressed concern during the lead-up to the election that Hook had started to prepare administratively for a Marshall Government, including looking at options to introduce Marshall’s “Infrastructure SA” concept.

Hansen has emailed staff to tell them he is leaving Renewal SA to return to the US.

“Earlier this year I had a knee operation to address a running injury. And in March I turned 68. These two events allowed me to reflect on my priorities,” he wrote.

“Heather and I have absolutely loved our time in Adelaide and we feel we have accomplished much. But now is the time for us to reconnect with family in the States and make time for long overdue travel plans. We are very much looking forward to the next chapter in our lives.

“I have valued my time here at Renewal SA working with a high performing team who are passionate about making a positive difference to the way South Australians are able to live.

“It has been remarkable working with three Ministers over this period; Patrick Conlon, Tom Koutsantonis and now with John Rau–who have all shared the passion and commitment to making South Australia an even more remarkable place to live and work.

“We have made significant progress, since our establishment in March 2012, in delivering a vision for an inspiring urban future for all South Australians, however I firmly believe the organisation requires additional government support and focus to allow it to achieve its full potential.

“I congratulate you all for the commitment and drive you have shown as we have worked towards our objectives and the visions we share for our wide ranging renewal projects. What I will miss most is the relationships and friendships I have formed and I will take many special memories home with me.

“I wish you all nothing but the best as the organisation evolves and continues its great work on behalf of the South Australian Government.”