Data centre developer DC01UK has sold its South Mimms site in Hertfordshire to global operator Equinix in one of the largest UK infrastructure and real estate deals in recent years.

The sale paves the way for a £3.9bn investment to build one of Europe’s biggest and most advanced data campuses, consisting of three big builds.

Covering 85 acres off the M25, the vast site now rebranded by Equinix as the Hertfordshire Campus will deliver more than two million square feet of data centre space to support the surging demand for cloud and AI services.

The deal marks a major milestone for the UK’s fast-growing data infrastructure sector following the government’s move to classify data centres as Critical National Infrastructure last year,  a decision influenced by the scale of the DC01UK project.

James Craig, director of DC01UK, said: “This is a landmark moment for the UK and a powerful example of local entrepreneurship driving national innovation.”

He added: “We’re proud to see our vision taken forward by a global leader committed to delivering it to the highest standards.”