It may be 800 years or more since the Vikings ceased their raids into Britain in search of gold to plunder, but another Viking raid of sorts will take place this summer when two of Scandinavia’s finest come to the Olympics with firm hopes of taking precious metal from their British rivals.

Most well known of the pair is Denmark’s Lotte Friis, who over the past couple of years has established herself as the only woman who can realistically challenge Rebecca Adlington for the 800m freestyle crown. Meanwhile Sweden’s Sarah Sjoestroem has placed herself firmly amongst the contenders in three events and will be matched against Fran Halsall in two and Ellen Gandy in one, placing herself directly against two more of Britain’s brightest medal hopes.

The threat from Friis is already well known, with the 2009 world 800m champion the only swimmer to stay within touching distance of Adlington in Shanghai last year. She believes it will be another titanic battle this summer: “I think it’s a really close race, it could be anybody’s, and I like that because you don’t know who’s going to win until the clock stops” she says.

“But Rebecca is the favourite going in, she’s the world champion, she’s the Olympic champion, and she has the home crowd advantage so obviously she’s the girl to beat.”

Not that having the underdog status is off-putting for the Dane, who is relishing the chance to race with reduced pressure. “I like the fact that I’m not the favourite because that gives me time to focus only on myself; just focussing on what I need to do to swim my best. Hopefully that will be enough to get a medal and who knows if that will be gold silver or bronze.”

On form it would be easy to ink in the names of Adlington and Friis for the top two places at the Olympics, even if the order remains uncertain, but Friis refuses to see it that way. “I feel a little bit like I’m under pressure – that I’m going to win a medal no doubt about it, but I know how little it takes for unknown swimmers to get a medal” she explains. “I did that in Beijing; no-one expected me to take a medal and I still did, so I’m still looking out and not expecting anything at all because you never know what could happen”

And there it is; a parallel to be drawn between the experiences of Friis and Adlington following their gold medal winning exploits of Beijing and Rome, with the Danish public heaping expectation onto their champion in the wake of her 2009 triumph, much as the British suddenly saw an Adlington victory as inevitable post-Olympics.

“We are a really small country and swimming is not that big in Denmark, but in the Olympics, it always blooms and becomes one of the biggest events and with me taking a medal in the big competitions in the last few years, people are looking to me to take a medal, and I start feeling that pressure” says Friis, not that her rivalry with Adlington goes unnoticed, perhaps unlike the reverse situation in the UK. “Already back home people are talking about me and Rebecca against each other, because it was so close in Shanghai so of course they are expecting and are ranking me as a gold medal candidate, but we will see”

“I do feel like people are saying ‘yeah, Lotte is going to win a medal’ as when I got back from Beijing and Rome, everyone was so excited because it was new, but now it’s kind of old news.”

It is from there that the pressure arises, and with such a strong record in the last four years, it only intensifies inasmuch as her success becomes a given. “I felt like when I got back from Shanghai, people were like ‘oh yeah, Lotte won two medals, she was supposed to do that’ where we had Jeanette [Ottesson] who won the gold in the 100 freestyle and people were jumping up and down for her.”

An Olympic gold would certainly have people taking notice however, but with Friis not having swum and 800m fully rested in 2012, it won’t be until the Games themselves that we see how close the race will be. Regardless of the outcome it promises to be one of the best battles of the Olympics in what is the longest pool race in the women’s programme.

Meanwhile, at the other end of the distance spectrum, Sjoestroem has been cutting a swathe through the 100 and 200m freestyle events in the last 6 months, having already established herself as a force to be reckoned with over 100m butterfly by winning the world title in 2009 in a world record time. While that mark, aided by the now defunct Arena X-glide suit, remains out of reach, the 18 year old Swede has shown herself to still be at the top of the tree in the textile era, recording a time of 56.79 at the Olympic test event to sit atop the world rankings, almost half a second ahead of Gandy in second.

Not content with that she also posted a 1:55.23 200m freestyle in London to add to a 53.05 blast in the 100m at the very end of 2011. That swim had ranked officially the best ever in textile until the remarkable recent performance of Ranomi Kromowidjojo, but Sjoestrom is still second in the world in both events for 2012.

Remarkably her test event performances came in a period of intense training. “I just came back from a training camp so I was not really prepared to do well, to do a fast race” she said, with the implicit warning for her rivals that entails.

But her recent surge to the top of the world can be traced back to results in Shanghai last year, where Sjoestroem finished in fourth place no fewer than 3 times. “I only really had first places before” she explains, recalling a series of results that saw her retain the European 100m fly title in 2010 to follow up her 2009 world championship win, “so I needed to know how it felt to come fourth – it’s good to know for the Olympics what can happen – you can learn more from your defeats.”

“I needed that motivation and I did much better training after Shanghai” she continues, “so it was very good for me to have that experience.” That improved training has also seen a revision to her freestyle stroke, part of the reason she now sits near the top of the world rankings

“At the last Olympics I wasn’t even qualified for the relay in the freestyle events. Now I’m first in the 100 and 200 free in Sweden – I’m much faster now having changed it to swim properly!”

But whatever the threat the Sjoestroem poses in London, Britain can take some credit for her improvement given that she has been guided through her swimming career by an English coach, Carl Jenner.

Jenner hails originally from Brighton and swam for Haywards Heath, before emigrating to Sweden with his wife in 1993. He started coaching at the Södertörns club, which also produced Stefan Nystrand, in 1995 and was head coach by the time a certain young swimmer joined the club.

“Sarah came into our programme as an 8 year old and we started to see this name cropping up in competitions quite often, so we had a look and have tracked Sarah through the squad system, to where she is now” Jenner recalls, elaborating on her freestyle progress by adding “we’ve changed Sarah’s technique and there’s been a progression in the number of metres Sarah now swims compared to 2008. A lot of those metres are freestyle, so while she’s always been a good freestyler, she has developed into an excellent freestyler.”

An excellent freestyler with a real chance of standing on the Olympic podium three times. Friis of course is targeting the medal places as well, but success for the Scandinavians could spell disappointment for Britain. Friis puts it more bluntly. “I’m hoping to spoil the British party”, she says with a smile, before remarking on the sentiments that stalk her on these shores, where people inevitably and understandably, have a parochial eye on the medal places. “When I talk to the British press it’s always “Do good but not too good!”