The network site at Cable & Wireless (C&W) is now back up and running following yesterday’s raid at the supplier’s facilities which left customers including Sainsbury’s and Ordnance Survey struggling to cope as web sites were unavailable.

It is understood that thieves broke into C&W’s facility in Watford, north London at 1am on Thursday morning allegedly looking for scrap metal, as the police had previously visited the facilities as part of an inquiry into scrap metal theft.

"Cable and Wireless have experienced unforeseen network issues that have regrettably had an effect on a number of our customers, but service at our facilities is now back up and running,” said a C&W spokeswoman.

“Emergency engineers are out on the field to investigate the issues and are working to restore full service to our individual customers," she said, without giving expected timelines as to when service will be fully restored to C& W's entire client base.

The network site then went offline at 1am yesterday after thieves reportedly stole vital equipment, which is also said to have affected the Financial Times web site. The FT was said to be running on backup facilities in the US, as it was unable to publish new articles or update data.

According to C&W, no customer data was taken as the attack took place at an unmanned network site as opposed to its datacentre.

Other C&W clients relying on round-the-clock availability include insurance group Aviva, which signed an extension of its communications contract with the supplier in May for a further six-year period. The deal, worth up to £300m, aims to improve the group’s communication with its customers and generate “significant cost sa vings” without reducing its networking facilities.