Johnny Depp splashed out £125,000 on a limited-edition book for Amber Heard's birthday.

The 50-year-old actor forked out on the massive sum on a rare Ernest Hemingway short story collection called 'In Our Time' to mark his fiancée's 28th birthday on Tuesday (22.04.14).

The 'Pirates of the Caribbean' star also bought his literature-loving partner several 18th Century poetry books and a leather-bound diary, taking the grand total of his expenditure up to £140,000.

A source told The Sun newspaper: ''Johnny's head-over-heels in love with Amber and isn't scared of grand gestures to show just how much he appreciates her. He went all out for her birthday, sourcing rare books that she'd had her eye on for quite some time.

''He then went with her to pick them up at the shop, making out that it was a complete surprise that they happened to have them in stock.''

The lovebirds, who got engaged earlier this year after meeting on the set of 'The Rum Diary', were spotted snapping up the vintage tomes in New York City, before heading to the exclusive Bowery Hotel.

Johnny is said to have pulled out all the stops to give Amber an evening to remember, arranging for roses to be laid out in their suite and a string quartet to play in the background during dinner.

The insider added: ''Johnny's so crazy about Amber that people in his inner-circle wouldn't be very surprised if they had already married in secret and just don't want to announce it officially yet.''

Johnny separated from his long-term partner Vanessa Paradis, the mother of his children Lily-Rose, 14, and Jack, 11, in the summer of 2012, and has been smitten with Amber ever since.