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Incident

Guy's and St Thomas': heatwave cooling failure takes down both data centres

Air conditioning tripped at both trust data centres on the UK's record-heat day. Clinical IT went down and the trust ran on paper for weeks.

Sources checked when written 26 September 2026

TierData-centre cooling failed and the trust ran a 'Paper Hospital' for about six weeks; clinical areas kept power. How tiers are assigned.

What happened

On 19 July 2022 (London peaked at 40.3°C) condenser high-pressure trips shut down cooling at the Guy's data centre, which reached 50.3°C; the St Thomas' data centre suffered disk and controller failures. The two sites were each other's backup, a design the trust's review said could not cover a shared environmental cause. Cooling concerns had been raised in 2018 and a £195k replacement request from March 2022 was still unapproved. The remote environment monitoring for St Thomas' was hosted on the storage network that failed, and email alerts stopped. The trust declared a critical incident and moved to a 'Paper Hospital'. Core clinical systems took about six weeks to recover, slowed by 371 interlinked systems. Activity fell to 64% of normal referrals and 68% of diagnostic tests. The same heat caused a cooling failure in a Google Cloud London zone that day.[1,2]

Documented harm

As of January 2023: one moderate harm (a patient could not be transplanted when organs became available), 20 low harms, no deaths or severe harm identified; the harm review remained open.

What it teaches

Sources

  1. Review of the Guy's and St Thomas' IT Critical Incident — Final report from the Deputy Chief Executive Officer. Guy's and St Thomas' NHS Foundation Trust, January 2023. Primary Official report · link checked 2026-09-26
  2. Incident: cooling related failure in one of our buildings that hosts zone europe-west2-a. Google Cloud Service Health, 19 July 2022. Primary Official report · link checked 2026-09-26

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