Telecity data center owner Equinix has 'fessed up to a "brief outage" that knocked 10 per cent of BT internet subscribers offline in the UK as well as a number of other providers on the morning of 20 July.

A spokesman from the group, which slurped up Telecity for £2.3bn in 2015, confirmed that the outage occurred at Equinix's LD8 site in London's Docklands. The company has nine server warehouses in the capital that service more than 600 businesses.

In an email to Equinix customers, seen by The Register, the company said it experienced a power issue "with one of our UPS system at 8/9 Harbour Exchange (LD8)" this morning.

It said the company was carrying out a full investigation into the incident to identify the root cause of the fault and will "provide a further update once the investigation is complete".

One customer said: "This is the root cause of the BT outage. I suspect their connection to their peers failed to come back (a broken switch or something) and so they've had to rely on inadequately provisioned transit outside of Telecity."

It is not the first time Telecity has experienced power issues. Last year it had a major problem at its Sovereign House data centre, also in the Docklands.

Engineers spent two days fixing a power outage there last November after a failed repair job resulted in the primary and backup power supplies going down.

A spokesman from the company said: "Equinix can confirm that we experienced a brief outage at the former Telecity LD8 site in London earlier this morning. This impacted a limited number of customers, however service was restored within minutes. Equinix engineers are on site and actively working with customers to minimise the impact."

A BT spokeswoman said the power issue affected around 10 per cent of internet usage - meaning one in 10 attempts to connect to the website they want to go to may fail.

She apologised to customers for the outage following the power issues: "The issue has now been fixed and services have been restored.” The very next day, it happened again. ®