Following the successful marketing of the six-acre Shire Hall site in central Cambridge – resulting in bids from more than 30 organisations - councillors agreed developer Brookgate as their preferred bidder.
Cambridgeshire County Council met on May 14 and discussed the results of a three-stage selection process that included a councillor working group.
The merits of the four final shortlisted bids were debated which included their proposals on how the Castle Mound and the civil war earthworks, the site's major heritage assets, and access to them, would be protected or enhanced.
Brookgate was agreed as the council's preferred bidder to lease the site and further negotiations will now begin between the developer and the council to agree the full terms, including the length of the lease - expected to be for a term of between 30 and 40 years.
The county council hopes to move to a new £18million headquarters in Alconbury Weald, by the end of next year.
Brookgate, which is responsible for the CB1 development and the developer of the area around the Cambridge North station, in Cambridge, has proposed subject to planning permission, a hotel and prime office accommodation on the site.
The lease arrangement does mean the site remains in public ownership, confirming thr county council's commitment to enshrine continued existing public access to the site in the final agreement.
Cllr Steve Count, leader of Cambridgeshire County Council, said: "We are very aware of our responsibilities to safeguard and enhance public access to the heritage assets on the site - which has been an important part of the selection process, but we are also mindful of the need to make the very best use of our assets in order that we can re-invest resources in the essential frontline services which the people of Cambridgeshire rely upon.
"This potential lease arrangement looks likely to exceed figures outlined in our business case, and see the value of our asset enhanced, but still retain ownership of the site for future generations - which strengthens our original decision to vacate the site."
Cllr Josh Schumann, chairman of the council's commercial and investment committee, said: "We received a range of interesting and varied proposals throughout the marketing process which reflects the unique opportunity we were offering.
"I am pleased that members have resolved to proceed to the next stage which keeps us on track to realise our ambitions to relocate to both a smaller headquarters in Alconbury and through our network of 'spoke' locations, develop much closer working arrangements with the communities we serve."