Police in Oxfordshire county in Britain accidentally ruined the surprise that a farmer had put much effort into preparing for his wife.

Mr Murray Graham had written his wife's name in huge letters - SUE X - on his field as a romantic gesture, but the National Police Air Service (NPAS) spotted it and posted a picture of it online on Thursday (Nov 2) before she could see it for herself, reported The Telegraph.

The aerial photo went viral with the hashtag #FindSue and the Internet was roped in to help uncover the identity of the mysterious Sue.

Mr Graham, 49, revealed himself as the source a day later, after he was tagged in social media posts by friends.

He had been clearing the field of weeds early last week, when he decided to use the GPS system on his tractor to help him mark out the message.

"I had some leftover chemical and I thought I'd give it a go and see if I could put a smile on her face," he told The Telegraph, adding that he was pleased with the end product.

He rears 50 cattle and grows crops, such as wheat, on the farm.

Mr Graham, who has been married for 22 years, asked his helicopter pilot son George, 21, to take a picture of the 150m-long message from the air, but the police beat him to it.

Bournemouth University geography lecturer Andy Ford said the message on the 15-acre field was visible even from space and was captured on a satellite image.

"I'm quite surprised," said the farmer. "I didn't expect it to go national or international or even intergalactic."