The planned £3.5bn ($7.04bn) upgrade of cross-London Thameslink services took a significant step forward on Thursday when one of the train operators involved announced it had agreed to buy 44 new carriages for use on the route.

To be delivered next spring, the trains will form part of a fleet, to be operated by Southern Railway, that will run to destinations on the line to Bedford, north of London, instead of terminating at Blackfriars, as happens at present.