In the early 1980s, British Rail's shift to an air-braked network created logistical challenges for the Ministry of Defence (MoD), whose depot sidings had sharp curves that could not accommodate newer, long-wheelbase wagons.

To solve this, 50 vacuum-braked, 12-foot wheelbase "Pipe" wagons (built in 1961 under Lot 3335 to Diagram 1/462) were selected for conversion. Their drop sides were ideal for palletised loads. Modified at Shildon works in 1983 with air brakes and UIC double-link suspension, they entered service as general merchandise wagons under the TOPS code ODA, sporting a Carnival Red and Flint Grey Railfreight livery.

The ODAs successfully served the MoD network until the end of the Speedlink era. Between 1991 and 1993, they transferred to departmental infrastructure pools as ZDA wagons, wearing a red-and-yellow Satlink livery to move signalling equipment. Post-privatisation, surviving ODAs passed to EWS, running in wine red and gold until most were withdrawn by 2010.

Meanwhile, unconverted Lot 3335 wagons served various departmental roles—including the light-blue Project Mercury fleet—before vacuum-braked stock was phased out in the 1990s. Today, examples of both the ODA and original SOV variants are preserved on heritage railways.