The lights went out yesterday morning at one of the London telecoms hubs that carries internet traffic for the likes of BT, Sprint, Deutsche Telekom and Tiscali.

Telehouse, an IT managed services provider to telcos and internet companies, reported a power outage just as the working day was getting started. 

The company declined to say which of its 475 clients were affected, but UK ISPs ClaraNet and the London Internet Exchange are among the known casualties. 

Although the statement from the service provider said that the outage lasted from 08.18 to 12.20, ClaraNet's service status webpage reported the outage starting at 07.43 and continuing to affect the ISP's email and internet access services until 14.14.

The cause of the power failure, it would appear, was a dodgy cable. "One of the two power distribution units (PDU 2) in this room [TFM6] suffered from a power failure to one of the three-phase outputs, caused by a burnt-out cable connection," read a statement from Telehouse.

A statement issued in the afternoon read: "Power was restored to affected customers at approximately 12.20 and this was achieved without the need to isolate the PDU, thereby avoiding further customer disruption."

Telehouse engineers are investigating the cause of the problem and will prepare a post-event report, said a spokesperson.

So, presumably, right now there is an electrician looking at the burned out cable, sucking in air over his teeth and muttering "what cowboy put that in, then?"