Up to 200,000 visitors from around the world are expected to arrive in Kent over the next four days for the 140th Open Golf Championship in Sandwich.
The tournament at the Royal St George's course got under way at 0630 BST.
High-speed train services direct from London to Sandwich are running for the first time, with journey times cut from two hours 15 minutes to 80 minutes.
Traders in the town are opening early in the morning and late in the evening to gain maximum benefit from the event.
The Open was last held in Sandwich in 2003, when Visit Kent recorded 182,585 spectators and £17.6m additional spending.
This year is the 14th time the championship has been played at Royal St George's.
Southeastern estimates that up to 9,000 passengers a day will come into Sandwich station, which is being served by four trains an hour - two high-speed and two mainline.
Parking restrictions in the area are in place until Sunday, with drivers heading to the championship being advised by police to use the M2/A2 rather than the M20 even if their sat navs tell them otherwise.
A park and ride facility is open off the A256 at Barville Farm.
Kent Police's Chief Constable Ian Learmonth has promised The Open will be "a tremendous success" for the county.
Speaking during a visit to the course on Wednesday, he said everything was in place to make the event run smoothly.
Weather during the four-day event is forecast to be a mixture of sunshine, wind and rain.
The winner will receive the famous Claret Jug and a cheque for £900,000.