Private prototype. Facts from research on 2 to 3 October 2026; not yet reviewed for publication. Forms do not submit.

All schemes

Decision pendingEast of England, England

Former Mercure Hotel, Tylers Way data centre campus (Ark Elstree campus), Hertsmere

A full application for a data centre campus was validated on 24 December 2025 and no decision or committee date was found; it was not on the Hertsmere planning committee agendas for 23 April or 16 July 2026. Objection deadlines seen were early February 2026, but further consultation rounds are possible. [S1] [S2] [S7] [S8]

Key facts

Status
Decision pending (application submitted) [S1] [S2] [S7] [S8]
Decided by
Hertsmere Borough Council [S1] [S2]
Applicant
Ark Data Centres (promoter; applicant name on the application form not confirmed from the portal) [S3] [S4] [S6]
References
25/1781/FUL
Location
Site of the former Mercure Hotel, Tylers Way (off the A41 North Western Avenue), with adjoining land to the south east, Hertsmere, Hertfordshire, in the Metropolitan Green Belt, with Hilfield Brook flood zones 2 and 3 along the site (per objectors' document). [S1] [S2] [S5]
IT capacity
200MW [S2] [S3] [S11] [S6]
Buildings
Application: four free-standing data centre buildings (objectors' document and Save Hertsmere); Ark pre-application: up to six buildings [S2] [S3] [S11] [S6]
Investment (claimed)
GBP2bn (claimed by Ark, as reported) [S2] [S3] [S11] [S6]
Backup generators
Backup generators included; number not found [S2] [S6] [S12]
Cooling and water
Ark says outside air cooling and rainwater harvesting (claimed). Objectors state the application implies 764 million litres of water a year (campaigner figure; not verified). [S2] [S6] [S12]
Designations
Metropolitan Green Belt (application relies on grey belt policy per objectors); Flood Zones 2 and 3 along Hilfield Brook; Part within a groundwater source protection zone; Landscape Character Area 15 (Bushey Swards); Setting of listed buildings and a Jewish cemetery (objectors' claim) [S2] [S3]
Previous use
Former Mercure Hotel (previously owned by DC01UK according to a BisNow report cited by DCD; not verified) [S2] [S3]
Environmental assessment
Not established from sources found [S2] [S3]

Timeline

  1. 1 November 2025
    DCD reports Ark plans a 200MW campus at the former Mercure Hotel site (up to six two-to-three storey buildings, GBP2bn) [S3]
  2. 4 November 2025
    Ark pre-application consultation event, Hartspring Lane Community Centre; second event 27 November 2025 [S4] [S6]
  3. 24 December 2025
    Application 25/1781/FUL validated (documents dated 15 to 23 December; registered in council weekly list 15 to 28 December) [S1] [S9]
  4. 27 January 2026
    Letchmore Heath Village Trust publishes its formal objection; objection deadline stated as 6 February 2026 [S2] [S10]
  5. 9 February 2026
    Save Hertsmere data centre page last modified, objection form live [S11]
  6. 23 April 2026
    Hertsmere planning committee meeting: 25/1781/FUL not on agenda [S7]
  7. 16 July 2026
    Hertsmere planning committee meeting: 25/1781/FUL not on agenda [S8]

Politicians and organisations

  • Letchmore Heath Village Trust (formal objection, template letter)
  • Save Hertsmere (objection form)

Claims

Claims by developers, campaigners or councils, recorded as claims and not checked as fact.

  • Ark Data Centres (via DCD, Data Centre Magazine, Little Bushey Community news item) (developer): 200MW campus; 250MVA power from 2028; GBP2bn; first building by 2029; 100% renewable energy; 235 jobs (pre-application) [S3] [S12] [S4]
  • Applicant's documents as quoted in the Village Trust objection (not checked against the application) (developer): Application requires 1,910 GWh of electricity a year at a PUE of 1.3 [S2]
  • Letchmore Heath Village Trust formal objection, 27 January 2026 (campaigners): The scheme would equal 63% of Hertsmere's current annual carbon emissions; uses 764 million litres of water a year; building height 38.95m; inadequate grey belt case; harm to heritage; 24/7 noise [S2]
  • Save Hertsmere (campaigners): Four towers exceeding 39m, 137,000 sqm, construction 9 to 10 years [S11]

Campaigns

Sources

  1. [S1] Planning Application for Site Of Former Mercure Hotel Tylers Way Watford (25/1781/FUL). Planning Portal aggregator (planning.org.uk), 24 December 2025. Level 7 source.
  2. [S2] Objection to 25/1781/FUL Redevelopment and clearance of site to deliver data centre. Letchmore Heath Village Trust, 27 January 2026. Level 6 source.
  3. [S3] Ark plans 200MW data center campus in Watford, UK. DatacenterDynamics, 1 November 2025. Level 5 source.
  4. [S4] Data centre consultation opens. Little Bushey Community, 3 November 2025. Level 6 source.
  5. [S5] Former Mercure Hotel data centre project site. Ark Data Centres. Level 3 source.
  6. [S6] Ark Data Centres to Convert Watford Hotel Into 200MW Campus. Data Centre Magazine, 3 November 2025. Level 5 source.
  7. [S7] Hertsmere Planning Committee agenda, 23 April 2026. Hertsmere Borough Council, 23 April 2026. Level 1 source.
  8. [S8] Hertsmere Planning Committee agenda pack, 16 July 2026. Hertsmere Borough Council, 16 July 2026. Level 1 source.
  9. [S9] Planning Applications Registered Between 15/12/2025 and 28/12/2025. Hertsmere Borough Council, 2025-12. Level 1 source.
  10. [S10] DATA CENTRE: LHVT objection to data centre 25/1781/FUL. Letchmore Heath Village Trust, 27 January 2026. Level 6 source.
  11. [S11] Data Centre - Save Hertsmere. Save Hertsmere, 9 February 2026. Level 6 source.
  12. [S12] How Ark Data Centres is Turning a Hotel into a Data Centre. Sustainability Magazine, 2025-11. Level 5 source.