An unscheduled software upgrade was what caused some 40,000 computers at the UK government's Department for Work and Pensions (DWP) to crash, the IT supplier EDS has announced.

Nearly 80 per cent of the department's machines were wiped out between 22 and 26 November after what a DWP spokeswoman said at the time was a "routine software upgrade".

Now it seems the upgrade was carried out on machines that were not scheduled for it. Unfortunately that is all EDS seems to be willing to share with the outside world, something that will be cause for concern since the DWP's IT contract with EDS and Microsoft has cost the taxpayer £2 billion.

EDS said the service disruption didn't affect benefit systems or the payment of pensions and benefits, although it did prevent computers from accessing core systems. Several steps have been taken to avoid a recurrence of the problem, according to EDS, including the enhancement of the company's change management procedures and increased checks by EDS' senior engineers and management staff when such upgrades are implemented.

It is with a certain amount of irony that the only mention of the system at the DWP on EDS website is the announcement that the project won "Public Sector CRM Project of the Year" at the the UK CRM 2004 Industry Awards.

The IT failure is just the latest in a series of computer failures. A benefit-payment card program from the Post Office, the Department of Social Security and ICL, fell apart after three years costing £300 million; software problems delayed the Swanwick air traffic control centre and have since been blamed for a near collision between two airplanes; disruption was wrought on thousands of people with travel plans in 1999 by the Passport Office's new computer system, and the National Probation Service's case-record and management system was abandoned in 2001 after it was revealed the project was expected to be two years late and 70 percent over budget.