The Hertsmere data centre proposed by Ark Data Centres near Watford has been deferred after councillors voted against determining the application at their meeting on Thursday 5 November 2026. The proposed campus on the former Mercure Hotel site at Tylers Way represents a reported investment of around £2.5 billion. Hertsmere Borough Council’s Planning Committee wants further information before deciding whether to grant permission.
The committee’s own recording of the 5 November meeting confirms the deferral. Members asked for more evidence from Affinity Water, further discussions about financial contributions under a Section 106 planning obligation, and consideration of the development’s height and design. The proposal was deferred on those grounds rather than approved or refused.
This is an important decision for a major infrastructure scheme in Hertfordshire and for other developers promoting large data centres on constrained sites. The debate went beyond whether the investment and digital infrastructure would be valuable. Councillors wanted greater confidence about local infrastructure, the effect of large buildings on neighbouring communities and the practical commitments that could be secured before permission is issued.
Why the Hertsmere data centre was deferred
The application, reference 25/1781/FUL, seeks full planning permission for a campus of substantial data centre buildings with associated power and water infrastructure, internal roads, security arrangements and landscaping. It covers the former hotel site and neighbouring land. The proposal has attracted considerable local attention because of the scale of the buildings and its Green Belt setting.
Planning officers had recommended approval, having weighed the economic and infrastructure benefits against identified planning harms. But members of the committee were not ready to complete that balancing exercise. During the discussion, several councillors raised concerns about the relationship between the development’s scale and its setting, including nearby homes and a Traveller site.
Water availability became a central question. One councillor specifically sought written confirmation that Affinity Water could supply the scheme while meeting other expected demand in the area. Officers responded that the cooling strategy could adapt, including greater reliance on air-based systems if the anticipated water supply were not available. Members nevertheless wanted the water position clarified before a decision.
According to BBC reporting of the meeting, Rob Silvester, from Ark Data Centres, told councillors: There will be no adverse effects on local water supplies.
Members were not prepared to rely on that assurance without further evidence from the water company.
The Hertsmere data centre debate also focused on what the local community should receive in return for hosting a project of this scale. Councillors questioned whether the proposed financial arrangements adequately reflected the development’s impacts and potential economic benefits. An officer explained that an additional financial contribution would need to be secured through a planning obligation rather than simply attached as a condition.
Section 106 obligations and local benefits
One significant part of the discussion concerned the possibility of negotiating further commitments with the developer. Officers indicated that delegated authority could be used to pursue a contribution, but members preferred to bring the proposal back once there was a clearer package to assess. The prospect of cross-party involvement in overseeing community benefits was also raised during the meeting.
That distinction matters. A planning committee is not simply deciding whether a developer should promise something useful. Any obligation relied upon to make development acceptable must be justified through the planning process and documented properly. Planning Geek’s guide to Section 106 agreements explains how these commitments operate and why they must be distinguished from ordinary planning conditions.
For the Hertsmere data centre, the unanswered question is therefore not just the eventual amount of a contribution. Members need to understand what any obligation would deliver, whether it addresses identifiable planning impacts, how it would be enforced and whether it changes the overall planning balance. The committee did not agree a final contribution or conclude that an acceptable agreement was already in place.
Height, design and effects on neighbours
Members also discussed the visibility and massing of the proposed buildings. The scheme involves tall, predominantly industrial structures on a site where landscape, neighbouring uses and the Green Belt are material considerations. Some councillors were concerned about how the development would be experienced from nearby properties, open land and sensitive locations.
The exchanges covered noise from data centre operations, including generators and their testing, and the effect on residential amenity. Officers referred to technical assessments and possible controls, while members questioned whether the existing information provided sufficient assurance. These are issues that may require more detailed technical explanation or design changes rather than a simple statement that impacts can be conditioned.
The Hertsmere data centre proposal illustrates a wider planning challenge for digital infrastructure. Data centres can provide strategically important computing capacity and investment, but their electricity demand, cooling systems, building bulk and local infrastructure requirements are unlike those of many conventional commercial developments. General support for the sector does not resolve the merits of an individual site.
What the committee actually decided
The recording provides unusually clear evidence of the procedural position. Towards the end of the debate, a motion was made and seconded to defer the application. The chair clarified that the committee wanted further information from Affinity Water, discussions about the Section 106 arrangements, and answers on height and design. Members then voted on a deferral covering the outstanding points.
After councillors were called individually to vote, the result was announced as carried. There was no vote granting planning permission for the Hertsmere data centre and no final refusal on the application. That matters because a committee deferral leaves the planning application live. It must not be reported as an approval simply because officers were recommending permission, or as a refusal because members expressed substantial reservations.
As at 9 November, the council’s committee meeting index lists the 5 November agenda without published minutes. The official video is sufficient to confirm the vote, but the eventual wording of the formal minutes and any later officer update should still be checked when available. The next scheduled Planning Committee meeting is listed for 26 November 2026, although that does not itself confirm when this application will return.
What happens next for Ark’s proposal?
The applicant and council officers have the opportunity to address the matters identified by members. That could include direct written evidence on water capacity, updated design information, and clearer proposals for legally secured contributions. Whether those discussions produce amendments or simply further explanation remains to be seen. The committee’s deferral should not be taken as a guarantee of approval at the next meeting.
The Hertsmere data centre remains a high-value test of how the planning system handles emerging digital infrastructure. Its eventual outcome may be locally specific, but the questions posed at committee are familiar to promoters elsewhere: demonstrate the availability of essential services, show how harm has been assessed, and explain precisely what is being secured for neighbouring communities. The decision stage is still to come.
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