another seven months—May 2003—before the entire fleet had entered service. The protracted and difficult introduction of the Juniper fleet is credited with influencing SWT's decision in April 2001 to replace the rest of its slam-door units with an order of 785 vehicles from the competing Siemens Desiro family. Withdrawal from service Even after the full complement of units had entered service, reliability remained so poor that in January 2004 South West Trains announced that they would withdraw the entire Class 458 fleet at the December 2005 timetable change in readiness to return them to lessor Porterbrook when the lease on the fleet expired in February 2006. At the time of the announcement the trains were only managing an average of between major failures, whereas the new Siemens Desiro () units—which had only entered service in October 2003—were already achieving an average of between faults, and the slam-door fleet had regularly managed intervals of circa . An additional 17 Class 450 units had been ordered to replace the Class 458 fleet, but as these new units would not be delivered for some time yet Porterbrook later agreed with SWT that the Junipers could stay in service on a pay-per-use basis past the original end of the lease. In a separate arrangement units 458001 and 458002 were transferred to Gatwick Express in September 2005 to act as a spare train for that operator, but they were returned to SWT in December 2006 without having been used. In addition to reliability problems, continued use of the Class 458 fleet was complicated by issues surrounding compliance with the Rail Vehicle Accessibility Regulations (RVAR) 1998. The Regulations, which mandate the accessibility features that vehicle designers and operators need to provide in order to meet the requirements of the Disability Discrimination Act 1995, were in the process of being formulated at the same time as the Class 458 fleet was being designed and the finished units accordingly received temporary exemptions from compliance on a total of 10 different points. The exemption relating to the size of the internal passenger information displays expired on 31 July 2006—having already been extended from 30 September 2004—and the Department for Transport declined to provide any further extension. SWT fitted replacement displays of a compliant size to eight units for use as stand-by stock, while the remainder of the fleet was placed in storage. Return to service In September 2006 the