Fragments of wheat DNA recovered from an ancient peat bog suggests the grain was traded or exchanged long before it was grown by the first British farmers.
The research, published in Science, suggests there was a sophisticated network of cultural links across Europe.
The grain was found at what is now a submerged cliff off the Isle of Wight.
Agriculture first appeared in the Near East and then spread along two main routes into Europe.
The accepted date of arrival on the British mainland is around 6,000 years ago, as ancient hunter gatherers began to grow crops such as wheat and barley.
The DNA of the wheat – known as einkorn – was collected from sediment that was once a peat bog next to a river.
Scientists think traders arrived in Britain with the wheat, where they encountered a less advanced hunter gatherer society.
The wheat may have been made into flour to supplement the diet, but a search for pollen and other clues revealed no signs that the crop was grown in Britain until much later.