American Beth Allen shot a final round of 67 to come from five shots behind the overnight leader Caroline Masson and claim her first professional title at the ISPS HANDA Ladies European Masters.

Allen fired five birdies on the front nine at Buckinghamshire Golf Club and picked up another on 14 before making bogey on 15 and setting the clubhouse target at 12 under par.

With the world number one amateur Leona Maguire tied for the lead after 17 holes and playing in the next group, there was a nervous wait before Allen was able to celebrate her victory. She was finally able to lift her first trophy in 11 years as a professional after the 20-year-old found the bunker behind the 18th green and failed to make a putt of around five feet to force a play-off.

Allen, 33, from San Diego, Califonia, said: “I wasn’t sure if it was ever going to happen so I’m really, really happy. I’ve waited a long time for this and I wanted it so, so bad, I’m ecstatic.”

She had finished second three times on the LET but her secret weapon was her new caddie, Sophie Gustafson. The 26-time tournament winner who has represented Europe eight times in The Solheim Cup and this year will be one of Carin Koch’s vice captains at St Leon-Rot in Germany, was on the bag advising Allen as she plotted her way around the Buckinghamshire layout.

05/07/2015. Ladies European Tour 2015. ISPS HANDA Ladies European Masters, Buckinghamshire Golf Club, Denham, England. July 2-5. Beth Allen of the USA and her caddie Sophie Gustafson during the final round. Credit: Tristan Jones

“Honestly, I feel like I just showed up and I didn’t have a lot of expectations because I finished second here in 2012 and haven’t made a cut since,” said Allen. “I thought, well, I’ll do my best and enjoy it and today. I got off to a really good start and thought maybe this can happen and Sophie kept me grounded. I ended up getting it done, so I’m really happy!”

Gustafson knew the right things to say at the key moments, but a clubbing decision on the par three 18th tee cost the less experienced Maguire the chance to win the title.

Handling the disappointment like a professional, Maguire explained: “I knew it was tight coming up 18 and we didn’t really know where the wind was coming from. I thought it was downwind, dad thought it was into the wind and it was probably the wrong club off the tee but I’m very proud of the way I played all day. Going out at the start of the day I would have taken that so it’s been a great day.”

Thailand’s Nontaya Srisawang ended shot further back in third place after a solid 72 and she said: “I’m really happy with the result today because I’ve been working hard for a while here to get into this position. I finished in the top three, so maybe I can qualify for the Open. It was a little bit exciting with pressure but I tried to focus on my game.”

The overnight leader Caroline Masson slipped back into a share of fourth place with Nicole Broch Larsen of Denmark and Australian Rebecca Artis after a 75, while four players ended a stroke further back in tied seventh.

Finland’s Noora Tamminen, Anne-Lise Caudal from France and the evergreen Englishwomen Trish Johnson and Dame Laura Davies ended on eight under par.

Johnson holed a bunker shot on 18 for a 66, while Davies recorded her 11th hole in one on the seventh using an 8-iron in a round of 67. She said: “It’s more Solheim Cup points, which is what I wanted, to show Carin I’m still playing well and could be an asset to the team.”