Accordingly, the line was ceremonially opened amongst great celebration on 17 December 1877, and to ordinary public operation the following day. There were six mixed (passenger and goods) trains each way, Monday to Saturday. It was a single track of standard gauge, using Vignoles (flat-bottom) rails. The "one engine in steam" system of operation was to be used and there was one intermediate station at Somerford (later named Great Somerford), which did not have goods facilities at first. The junction with the GWR main line was at Dauntsey, between Swindon and Chippenham, where branch trains had a bay platform. Branch trains did not run beyond Dauntsey; there was a short length of loop siding alongside the branch line at Dauntsey, used for running round passenger trains. The line was 6 miles 4 furlongs and 1½ chains (10.5 km) in length; there was a tunnel at Malmesbury, and the station there was on Gloucester Road just beyond Stanes river bridge. The construction had cost £76,565 so far—the final cost was to be £87,094.
