Thameslink’s 700108 became the first Class 700 Desiro unit to enter passenger service earlier this week.
The maiden service was the 10.02 from Brighton to London Bridge on June 20.
The Class 700s are being eased into passenger service on the Brighton to Bedford route before being rolled out across the network.
Once the Thameslink programme is complete, Govia Thameslink Railway (GTR) will operate 24 trains an hour through the Thameslink core between Blackfriars and St Pancras International.
GTR’s engineering director Gerry McFadden said: “We are thrilled that our new Thameslink train is performing well. In future, as the train continues to prove itself, we will begin running it across London to Bedford.
“Ultimately the train will give passengers much-needed additional capacity with longer trains throughout the rush-hour, creating at least 1,000 extra standard class seats.”
The Class 700s will be the first trains in the UK to use ETCS signalling overlaid with Automatic Train Operation (ATO).