DC01UK, South Mimms
Equinix
Outline permission only. The council cites 87,000 sq m of floorspace; no IT-load or grid-connection figure has been verified. DC01UK announced the sale of the 85-acre site to Equinix on 30 October 2025, and the transaction was confirmed by Equinix's adviser, BNP Paribas Real Estate.
Key facts
- Operator / developer
- Equinix
- Location
- South Mimms, East of England, United Kingdom
- Status
- Approved
- Facility type
- Data centre
- AI relevance
- Not stated
- Construction jobs
- 500
- Permanent jobs
- 200
Power & grid
- Network operator
- National Grid (transmission)
- Grid connection date
- 1 October 2029
- Grid position
- 400 MVA reservation via Elstree (Letchmore Heath) substation; connection targeted Oct 2029
- Power
- No IT load or electrical demand figure has been published. The developer states a power reservation of 400 MVA from the transmission network via the Elstree (Letchmore Heath) substation, with connection expected in 2029. MVA measures apparent power and is not directly equivalent to MW, so no capacity figure is recorded here.
- Heat reuse
- Heat reuse not being pursued, per planning documents reported by Computer Weekly.
Planning
- Council
- Hertsmere Borough Council
- Planning route
- Local planning (TCPA)
- Planning decision
- Outline planning permission granted by planning committee
- Decision date
- 23 January 2025
- Green belt
- Yes
- Land area
- 34.4 ha
- Recorded objections
- 5
- Recorded support
- 8
Benefits vs drawbacks
Benefits
£2m for new and existing bus routes; cycle hire expansion; path and crossing improvements; contribution to local employment and skills. 54% of the 85-acre site kept as green open space.
Timeline
Reality Score
Sources
- Data centre in Hertsmere given outline permission by planning committee
Primary record · Hertsmere Borough Council · 2025-01-23 · accessed 2026-08-12
- Data centre in Hertsmere given outline permission by planning committee
Secondary source · Hertsmere Borough Council · 2025-01-23
- DC01UK delivers major UK infrastructure deal with landmark sale
Secondary source · DC01UK · 2025-10-30
- Advisors on landmark £3.9 billion UK data centre investment
Secondary source · BNP Paribas Real Estate
- DC01UK: Everything you need to know about the UK government-backed Hertfordshire mega-datacentre
Secondary source · Computer Weekly (secondary)
Last verified
27 September 2026
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