In response to continued fears over terrorist attacks, Guardian IT has set up a 55-mile broadband fibre-optic ring around London.

The ScaleNet ring targets City firms that wish to store data outside the Square Mile. It is linked to Guardian IT's Docklands and Old Street sites, where users connect to a data centre in Hounslow.

Many firms have been keen to store data outside city centres following the 11 September attacks. The network was launched last week and asset management company Legg Mason Investors was signed up as its first customer.

"We already use Guardian IT's data centre for business continuity and web and data server hosting. Our equipment and data is at the Hounslow site and we use ScaleNet to get to the data centre more efficiently," said Mike Hinden, IT director at Legg Mason.

Services available include hosting mirrored data systems and using the data centre as a disaster recovery site.

"The ScaleNet ring now allows companies to use the Hounslow data centre for the affordable outsourcing of IT productivity," said Stephen Bean, marketing director at Guardian IT.

Hinden added that Legg Mason's overall costs had increased when it started using ScaleNet but that the business benefits outweighed this. "It vastly reduces our business risk," he said. "Taking on this service was a business-generated decision."

But the outsourcing of critical business data raises security issues that must be addressed before users pass over the data.

"We do not have any security concerns because the whole network is firewalled. Guardian IT does not have access to the data and in our industry outsourcing services is a norm," said Hinden.

"Since the 11 September attacks we have adjusted our marketing because many companies have asked us whether it is possible to have data stored in a centre well outside London," added Bean.