A spokesperson confirmed on Wednesday that Orange’s unnamed partner had had a "problem with a fibre-optic cable".
Orange’s customer services systems also appear to have been affected by the outage, as calls to that service are "routed via this part of the core transmission network".
O2’s network in London and the South East had a major outage today (Thursday) following a fibre-optic break near one of its switching sites in London.
Customers in London and the South East variable signal reception until a complete outage this morning as the O2 network in the region went haywire.
O2 has now done a temporary workaround which should mean all its customers have full service.
The disruption couldn’t have come at a worse time, with travellers stranded by a terror alert at the UK’s airports piling extra traffic onto the network.
It has been reported that O2 call centre staff have told customers that the network was performing "selective disablements”.
An O2 spokesman said the problems are down to three breaks in BT fibre-optics near one of the company’s sites in Leytonstone, London. Repairing the cables is a delicate job, he said, but the firm hoped to have a better idea later today of when the cables would be repaired.
In the meantime, he said, the company had temporarily rerouted traffic, and all customers should now have full service.