London's tube network moved a step closer to hosting mobile signals, with an emergency phone network now up and running.

'Airwave' allows seamless integration with normal networks for those involved in keeping the Tube safe and running, using Tetra technology.

The 125 underground stations have all been linked into the Aiwave system – which is costing the taxpayer a £107 million.

Needed

The need for such a system was brought to the fore by the London bombings of July 2005 which saw three stations attacked by terrorists.

Two weeks after the attack John Charles de Menezes was shot by police, who feared he was a terrorist; although it later turned out that the Brazilian national had done nothing wrong.

A working seamless communications network would have been a useful tool for the emergency services in both cases.

The project was scheduled for a March 2009 start, but has been completed ahead of schedule.

The possibility of extending mobile networks to underground trains has long been mooted, although concerns over terrorists using phones as detonators remains a fear, despite a successful implementation in Hong Kong.