Leon Smith is the man behind British tennis

But the brains behind Team GB's first Davis Cup victory in 79 years wasn't Andy Murray or even his brother Jamie.

Instead, it's the man Judy Murray calls her third son – the coach who once took on the responsibility of washing Andy's socks before he was even a teenager.

More than a few eyebrows were raised when Leon Smith was appointed captain of Team GB back in 2010 – many believed the job should have gone to former US open finalist Greg Rusedski.

A former junior player, Smith failed to make the step up to the professional game.

The appointment surprised the man himself, with the Glaswegian leaving school without any qualifications to embark on a career as a tennis coach.

But Smith's life changed when Judy Murray asked him to coach her 11-year-old son Andy in Dunblane – and the Scots have taken an incredible journey together since.

Andy has since admitted that, at the time, he thought his new coach was 'cool' because of an earring he wore – an earring which is still a great source of amusement to the pair now.

And that coming together was not only the start of a great friendship, it was also the start of Smith becoming a world-class manager and Andy a tennis great.

An impressive strategist, Smith knew the key to Davis Cup success was harnessing Andy's talent without allowing the team to feel like a one-man band.

In his first match, he saved Britain from relegation to the lowest tier with a 5-0 win against Turkey.

He then began the long task of raising the team's ambitions and commitment, with the key to it all making sure Britain had a team spirit strong enough to compete.

Smith said: "If you are going to have success as a team. it's absolutely essential everyone feels equal.

"You have to train with spirit and each player has to put the team first, they have to know they are all playing their part even if they aren't actually competing on the court.

"If you tell someone they aren't going to play and their performance dips in training, we are all in trouble because the standard of training then dips.

"Each team member has to support one other."

Those sentiments were echoed by Dom Inglot, who was left on the sidelines when Team GB won the Davis Cup by beating Belgium back in November.

He said: "Leon makes every member of the team feel equally important. As a player you want to play for someone like that – someone who really treasures your input no matter if it's on the bench or on the court."

There is no doubt Smith's relationship with both Andy and Jamie Murray has played a huge part in the team's subsequent success, with Smith believing the two brothers deserve huge credit for their commitment.

He said: "I am really fortunate with both Andy and Jamie that they fully understand the importance of a team environment.

"Their mother Judy, for those two boys, has always made sure they value being part of a team.

"There is no ego with them. Andy is the superstar but when he comes in, he is just one of the boys.

"He respects every team rule and every team value. That makes my job a lot easier in making sure everyone feels equal."

After the match against Turkey, Smith's enthusiasm, dedication and careful man-management saw GB win 11 of his first 13 matches in charge – and reawaken home passion in the competition.

Such was his success with team selection, tactics and preparation, he began to draw comparisons with football managers Sir Alex Ferguson and Arsene Wenger, as well as rugby union great Sir Clive Woodward.

Smith continued: "I always had the aspiration to win it, but I knew I had to build things step by step. We agreed as a team a way we would work, how we would prepare and how we would grow.

"Andy wasn't playing in the early stages, but we won most of our matches and then Andy added a strong force to the momentum we had already built. That meant we could really challenge."

Roared on by a passionate support, Smith admits the feeling of seeing his team crowned champions was hard to explain.

He said: "It was quite incredible – surreal – and it took a long time to sink in for so many different reasons. One was the history. It had been 79 years, which is an awful long time to wait.

"But it had also been an incredible journey. We had got involved in Team GB when they were at such a low.

"Over six years, we worked so hard and I have known people like Andy and Jamie since they were children.

"To share that moment with those people who you have spent all you career with was very, very special."

Now Smith, is all set to begin Team GB's defence of the Davis Cup which kicks off against Japan on Friday at the Barclaycard Arena, in Birmingham.

Key to the contest will be Andy Murray's showdown with fellow world top-10 player Kei Nishikori.

The coach said: "It's going to be very difficult because this is the first challenge we have had where we are facing another top 10 player.

"Nishikori is a very, very good player. It is a big challenge for Andy, because this is a tough match. The other players aren't household names but they are good players.

"They have got a very talented group. It's going to be a challenge, but the good thing is that on paper we will be the slight favourites. We have got to capitalise on that.

"We have chosen the court and we have got an amazing, amazing home support. In Andy, we have got an incredible leader. I back us to get through."