The managing director of Thames Trains has praised the company's staff as they prepare to transfer to the new franchise holder, FirstGroup.
Michael Hodson says this month has seen the service at its most punctual for four years, with a 87.8% of trains arriving on time.
The achievement comes as the company's seven-and-a-half-year franchise comes to an end this month.
From 1 April, FirstGroup will operate a two-year franchise.
Mr Hodson said: "In recent months our punctuality performance has improved considerably, which is a great credit to everyone in the company.
"We are proud to pass on to FirstGroup an operation that's now in very good shape for the future."
The managing director has written to the firm's employees thanking them for their hard work.
Thames Trains served passengers in west London, Berkshire, Oxford and the Cotsworlds, and the Kennet valley area.