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Iron Mountain LON-3 London Data Center

Slough, England, United KingdomUnder construction
Evidence
Planned critical IT
25 MW
Updated
Oct 28, 2026

LON-3 is the third Iron Mountain building at Slough and remains under construction. Its 25 MW is a future facility boundary; Q2 2026 reporting gives Q1 2027 expected completion, no pre-leased MW and $391.9 million total expected investment. None of those values is represented as operating capacity. Customer utilization, private contract terms and unreported project financing remain outside the verified public record.

Capacity

Reported capacity

Design

25 MW

Source

Reported capacity

Planned / design or future potential

25 MW

Source

Operating IT capacity: Not established in published records

A missing figure does not mean zero. Planned, utility and generation figures are not operating IT capacity.

Development

Development, permitting and phased deliveryUnder construction

LON-3 is the third Iron Mountain building at Slough and remains under construction. Its 25 MW is a future facility boundary; Q2 2026 reporting gives Q1 2027 expected completion, no pre-leased MW and $391.9 million total expected investment. None of those values is represented as operating capacity. Customer utilization, private contract terms and unreported project financing remain outside the verified public record.

Milestones (2)
Project-specific evidence refreshed and reconciled

Aug 29, 2026 · Recorded actual event

Completed · Status changed

Source not linked
LON-3 future phases expected to complete

Q1 2027 · Forecast / planned record

Forecast · Forecast completion

Source not linked

Participants

Iron Mountain Data Centers

Developer

Sources by role
Developer (1)

Capital & incentives

Capital claims and financing records may overlap. Their amounts are not added together.

Capital claims

Total expected investment

Transaction scope

$391,900,000

Source

Financing records

Investment commitment

$391,900,000

Jun 30, 2026

SEC-reported total expected investment for LON-3 future phases; not a debt financing or current facility valuation.

Parties & sources

Iron Mountain Data Centers (Borrower)

Sources (1)

Site & development

Location context

Actual

LON-3 | Slough | England | GB

Source

Location context

Actual

LON-3 | Slough | England | GB

Source

Project location

Actual

Slough, England, GB

Source

Expected completion

Forecast

Q1 2027

Source

Technical specifications

Renewable energy matching

Actual

Operator states 100% matched renewable energy where applicable

Source

Additional project facts

Lifecycle status

Actual

Construction

Source

Capacity basis

Actual

Iron Mountain publishes 25 MW for the LON-3 facility record boundary.

Source

Lifecycle status

Actual

Construction

Source

Capacity basis

Actual

25 MW is a future LON-3 build boundary. Q2 2026 reporting gives Q1 2027 expected completion and shows no pre leased MW; it is not operating capacity.

Source

Operator or developer

Actual

Iron Mountain Data Centers

Source

Current lifecycle

Actual

Under development

Source

Capacity classification

Actual

Future potential

Source

Capacity basis

Actual

25 MW is a future LON-3 build boundary. Q2 2026 reporting gives Q1 2027 expected completion and shows no pre leased MW; it is not operating capacity.

Source

Customer utilization

Actual

Not publicly disclosed

Source

Source refresh date

Actual

2026-08-29

Source

Sec capacity comparison

Actual

Q2 2026 leaseable and development schedules reviewed

Source

Preleased percent

Actual

0 percent

Source

Infrastructure & permits

Technical details (3)
Electric grid

Planned or represented

25 MW

25 MW is a future LON-3 build boundary. Q2 2026 reporting gives Q1 2027 expected completion and shows no pre-leased MW; it is not operating capacity.

Fiber

Planned or represented

Liquid-cooling-capable facility with redundant power and cooling, dark fiber, LINX access and GPU-ready configurations.

Cooling system

Planned or represented

Cooling and resilience architecture is described at facility or campus level; instantaneous draw and tenant utilization remain undisclosed.

Public-source research. Plans may change. See Evidence for sources and qualifications.

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