IT was the pool he learned to swim in as a determined seven-year-old.

This summer those very same waters could see Andrew Mullen become a world champion. The Glasgow-born swimmer - fresh from a successful year which saw him crowned a four-time European gold medallist at the age of 17 - is gearing up to compete at the 2015 IPC Swimming World Championships this July.

"It's exciting to have the world championships being held in my hometown," he says. "The venue is only 20 minutes from my house and it's also the pool I learned to swim in so there is a lot of sentimental value. I'm hoping my family and friends will be able to come along and cheer me on."

Mullen made his international debut as a 14-year-old at the 2011 IPC Swimming European Championships in Berlin. Competing in the S5 classification, he claimed his first major medals with silver in the 50m butterfly and 200m individual medley bronze. A year later he competed in the 2012 Paralympic Games, narrowly missing out on a medal as he finished fourth in both the 50m backstroke and 50m butterfly.

The 2013 IPC Swimming World Championships in Montreal brought two silvers and a bronze before Mullen went on to reach the top step of the podium in August with four golds and two silvers at the 2014 IPC Swimming European Championships in Eindhoven. Not bad going for someone who is still in his teens.

While Mullen, now 18, didn't get to compete at the 2014 Commonwealth Games as his disability class wasn't included he reckons the IPC Swimming World Championships, which take place at Tollcross International Swimming Centre from July 13-19, will help make up for that disappointment. The same venue which played host the Games, the event is set to attract 650 athletes from 50 countries.

"There was such a fantastic atmosphere at the Commonwealth Games and it would have been nice to be part of that Scottish team but I had Europeans to focus on instead," he says. "It will be good to race in front of a home crowd just like those guys did in Glasgow.

"Although I didn't get along to Tollcross itself, I did watch all of the swimming on TV and it was incredible. The highlight for me was Ross Murdoch winning the 200m breaststroke and that is one of the best races I've watched. My whole family got excited by that. Everyone always likes the underdog. Michael [Jamieson] is a super talented guy as well but Ross was just better on the day."

Mullen learned to swim at seven and began competing at club level when he was 11. His talents were first spotted at the age of 10 by five-time Paralympic champion Kenny Cairns who saw Mullen swimming in a Dundee gala and told the youngster he had potential to compete among the highest echelons of the sport. It was this meeting Mullen credits with giving him the self belief that he himself could one day become a world or Paralympic medallist.

He competes in the S5, SB4, SM5 disability classes. The prefix S denotes the class for freestyle, backstroke and butterfly; SB for breaststroke and SM individual medley. The numbers refer to the classification of an athlete's disability ranging from 1 (severe) to 10 (minimal).

Complications at birth resulted in amputations to both of his arms; Mullen was also born with a shortened left leg. "I have one functioning limb which is my right leg, I have two short arms and then my left leg is not functioning and also short," he explains.

Asked why swimming clicked over other sports and Mullen has a simple answer. "It was the first one I tried and I fell in love with it straightaway," he says. "I think it was the racing element that drew me to it. I just love being able to race. There is nothing better than that feeling of standing behind the block and racing the other seven guys in your final."

Away from the pool, Mullen is in his first year at Glasgow Caledonian University studying finance, investment and risk. The eldest of three children, he lives with his parents Katriona, a cardiac specialist, and Henry, a firefighter, in Newton Mearns.

"The cooking at home is too good to leave," he jokes. "I'm starting to learn to cook. I've recently changed my diet so I'm cooking lots of steamed vegetables, chicken and pasta. It's pretty basic but I'm getting there. Obviously I need to eat healthy for my swimming, but I'm always looking to find different variations to try and mix it up a bit."

He likes to keep life outside sport "pretty normal" and spend time with his friends. "It's almost like having two different lives," he says. "When I'm not swimming, I'm back to being a normal teenager hanging out with friends and playing my Xbox an obnoxious amount.

"My friends were all great about my medals but at the same time it's good to not have them focus on that. I like having that division between swimming and the rest of life."

Mullen is looking forward to the prospect of raising the profile of disability sport, thrilled and bashful in equal measures by his poster boy status. "It feels bizarre," he admits. "I have never done anything like this before but it's a real privilege. There are a lot of great swimmers in the team who have won far more medals than I have so it's an honour to be picked."

Chances are we will be seeing a lot of Mullen this summer. "I swim six events at a pretty decent level so I'm not sure if I will compete in all of those or drop it down," he says. "It will probably be quite a few. I will most likely target the 50m backstroke and 200m freestyle." Both are distances over which he has set European short course records.

Beneath his unfaltering drive and focus, Mullen has the endearing air of a young man who can't quite believe how life has panned out. "It's still hard to get my head around it," he says. "I wake up every morning and think: 'Wow, I can't believe I get to do this as my job'. I feel really lucky I get to do this. It's still all a bit surreal."

The 2015 IPC Swimming World Championships take place at Tollcross International Swimming Centre in Glasgow from July 13-19. Tickets are available from ticketmaster.co.uk/Glasgow2015