Twelve months. It's a very short time in rugby. But that was all it took between Rachel McLachlan picking up the oval-shaped ball for the first time and making her debut for Scotland.

With 24 caps to her name, the flanker is an integral part of head coach Brian Easson's squad and starting XV, including Saturday's Six Nations opener at home to England.

It's a far cry from being the first-year physio student who went along to her first rugby session at university "for the fun" of it.

That training session at Burnbrae was the first step on a path to the biggest stage in women's rugby - and a path that few could have predicted. However, there might have been some tell-tale signs that foreshadowed her meteoric rise.

Competing nationally for Scotland in age-grade judo competitions, she tried her hand at almost every sport she could think of before eventually becoming competitive in the martial art.

After moving west to start a physiotherapy degree at Glasgow Caledonian University, the constant travelling and training became arduous and she fell away from the sport.

"I lost my love for it a little bit," McLachlan says. "It was sad, but I recognised that wasn't me as an athlete. I didn't feel like I was giving it 100%.

"The goal with judo was always the Olympics and I thought 'am I good enough for these competitions?' I felt the answer was no. I already wasn't enjoying it, so I thought there was no point in me hacking away at something that I'm not enjoying."

With her judo career put to pasture, the Edinburgh native was left without a release for her bags of energy - until a friend suggested a taster rugby session with the university's women's side.

"My friend Katie, her family is really into rugby, so a few of us thought 'oh we'll go and try it'," McLachlan recalls.

"I just loved it. The running around, hitting stuff, it was right up my alley. I never had any preconceptions about it. I wasn't the most skilled rugby player to start with. I just did it for the fun.

"I loved the contact element - it's not a coincidence that I'm now a back row! I loved the tackling, the physicality. I didn't do many ball sports growing up, so it was an element I hadn't done before and I had to work at that."

However, McLachlan credits her years of martial-arts training for developing her breakdown skills - one of the many skills she has in her locker as an openside flanker - alongside her aggression.

"I know I'm maybe not always the nicest on the pitch, but that's part of the game," she admits. "I hope, when people come off the pitch, they know I'm a nice person!

"When I first started, I was probably a bit more carried away. Now I've reigned that in and it's more focused, more controlled aggression."

After a few months playing for her university side and the West of Scotland club, calls were made and she was fast-tracked on to a player development programme, initially joining the Scotland Sevens set-up.

Despite being involved in subsequent Scotland 15-a-side camps, she was still absolutely stunned to receive the news she would be involved in a match-day squad.

"I had been training with the squad in camps, but I didn't assume anything would come of it," McLachlan says. "It was a standard I'd never seen before, a real jump up. I felt quite out my depth.

"But I remember I was watching a Caley game, I was looking at my phone and I got an email through that said 'Scotland v Italy selection'.

"Caley had just won, but I didn't want to take the spotlight off them. We were celebrating and packing the stuff and I turned to one of my friends and said 'I've just been picked for Scotland'. It got out a bit, the coaches got told and it was mental."

Since that initial selection against Italy, the back-row has been ticking off the milestones. First match-day squad, first start, first Six Nations appearance. It would have been overwhelming had she had time to pause for breath.

"I was a bit clueless to be honest, just moseying along, happy to pick the ball up and run at things," McLachlan concedes.

Even in her very first cap, the momentous nature of the occasion didn't quite sink in.

"For my first cap, I didn't cry," she remembers. "I started 'o Flower of Scotland' too high. I was more focused on the fact that I was singing badly to be crying.

"For Canada, and so many games since then, I was bawling my eyes out. It's just such a special thing to be out there singing the anthem, especially when you see your family and friends in the stand.

"There's something about being Scottish, playing for Scotland, that is indescribable. It genuinely gives me shivers just talking about it. I know it sounds a bit cheesy, but this will be the thing that I do that I'll be most proud of in my whole life. I already know that."

It is a feeling that is shared across the board and an emotion that McLachlan pinpoints as a key part of the success of this Scotland side.

"We know that when we play, we're playing for each other, but we're also playing for Scotland," she explains. "The honour to pull on the jersey is massive in our team and nobody takes that for granted."

That unity has now propelled Easson's side to the Southern Hemisphere for the World Cup finals. For the squads self-proclaimed "annoying little sister", it will be a moment beyond her wildest dreams.

"As a young girl, I never thought that was a thing I would get to," McLachlan adds. "Being a female athlete has never been the same as being a male athlete. That change is coming now."