As a £20m bonanza awaits him, Murray toasts his long-awaited grand slam with a $6 soda

Andy Murray with mum Judy and the US Open trophy in New York (Getty Images)

He celebrated his triumph with nothing more excessive than a $6 lemon soda. But Andy Murray is expected to earn £20m from his entry into the Grand Slam club after America fell in love with the Scot who finally broke Britain's tennis hoodoo.

Sponsors, politicians and the world's media all clamoured for a piece of Murray, 25, whose draining victory over Novak Djokovic, pictured, to claim the US Open crown at Flushing Meadows could elevate the tennis champion ahead of David Beckham as Britain's most valuable sporting "brand".

The first British male winner of a Grand Slam for 76 years, Murray left his modest Midtown hotel room bleary-eyed yesterday, to relive his five-set triumph during a round of network US television breakfast interviews. He updated his Facebook page, telling fans: "Very busy day ahead, but I want to thank all of you for your support and belief in me. Didn't sleep very much last night!" Murray then paraded the trophy through Central Park for the cameras.

The champion, due to fly home last night, had discovered that being "king of the hill, top of the heap" in New York opens doors – particularly at the stylish Hakkasan restaurant which welcomed Murray and his entourage an hour-and-a-half after closing time, following his win under the lights. The party racked up a $6,448 in the restaurant's Ling Ling bar with a tip of $1,289. But the champion stuck to a lemon soda.

Throughout his media interviews, Murray maintained that his focus now remained firmly on winning more Grand Slams and becoming the undisputed world number one. Yet the presence of mind which caused Murray to search frantically for a watch given to him by the Swiss watchmaker Rado, to display for the cameras during the trophy ceremony, will stand him in good stead as hardball negotiations begin over maximising his new status.

Murray, who pocketed £1.2m for Monday night's win, earned £7.5m in the last 12 months from merchandising income and appearance fees, according to Forbes Magazine. He already has lucrative contracts with Adidas, Royal Bank of Scotland and Jaguar. Nigel Currie, of the sports marketing agency Brand Rapport, said: "Murray could realistically triple his off-court earnings to reach around £20m in the next 12 months."

In 2008, Murray joined the XIX Entertainment management stable, which guides David and Victoria Beckham as well as Formula 1 Champion Lewis Hamilton. However it is believed IMG, the global management giant, is seeking to lure the Murray with a counter-offer.

David Cameron said yesterday: "The forecast was made that the great summer of British sport was over, but Andy Murray has given us another immense prize to wake up to."