The high-speed Javelin train service serving the Olympic Park got off to an inauspicious start when the first official train departed five minutes late.
The Southeastern train company had designated the 7.04am from St Pancras station in London to the Park in Stratford as the beginning of the service.
But the 140mph Japanese-built train did not leave for Stratford until 7.09am.
One of those on the delayed train was a chef working in a hospitality area at the Park.
He has been travelling to Stratford from Luton via St Pancras for the last few days.
He said today: "Not one of my trains has been on time. It was 15 minutes late one day."
Once under way, the delayed 7.04am service raced to Stratford International Station in east London in under seven minutes.
Eight Javelin trains an hour will run between St Pancras and Stratford and Ebbsfleet International station in North Kent during the Olympics. Between 11pm and 1.59am there will be 12 trains an hour, with a half-hourly shuttle between Stratford and St Pancras between 2am and 5am.
The service will run until Sunday August 12 and will operate for the Paralympics from Wednesday August 29 to Sunday September 9.
Southeastern expects to transport 25,000 people an hour to and from Stratford. Those with Games' travelcards can use them on the Javelin service.