Some commuter train journeys take longer than they did before the Second World War, according to research published by the London School of Economics (LSE).
Researchers lead by Dr Tim Leunig, a reader in economic history at the LSE, compared timetables for services into London from before the war and the present day.
They found a journey into Waterloo from Surbiton took 17 minutes before the war. Last year the same journey took two minutes longer.
There was worse news for commuters travelling in from Wimbledon - their journey took three minutes longer than it had in 1930.
Mr Leunig said: "It is not that all trains are slower then they were in 1939 but some are."
He said the need to speed up commuter journeys into London was vital to the success of the economy.
"London to Wimbledon is three times as busy as the busiest inter-city routes," he said.
"The 20 busiest journeys in Britain are all short-distance journeys into London.
"London has become more important in the economy. Londoners are generally paid better and pay more taxes so it is in our interest to get more people into work in London."
A spokesman for the Association of Train Operating Companies said: "Passengers want reliability and punctuality over speed of services. While there might have been some journeys which were on paper faster before the war, they were not as dependable nor was there the choice of services that there is today. We are operating more trains on fewer tracks than we were before the war."
