Scotland face arguably their toughest assignment in international sevens when they join seven other aspirants at Twickenham this weekend in a bid to secure one of the three qualifying places that will earn core membership of the HSBC Sevens World Series next season.

This has come about because the International Rugby Board decided that the World Series needed to be changed from what many saw as a cosy club of 15 members, to one where entry was by merit. The top 12 in any season automatically retain their places on the world circuit for the following season while the next three places are determined by a qualifying tournament – London stages the first of them today – and the final position is at the discretion of the host country.

Scotland went into last weekend's penultimate leg of the World Series in Glasgow in joint 12th place with USA but blew their chances of automatic qualification by failing to reach the cup quarter-finals, unlike their American rivals.

"It is not a situation we wanted to be in," admitted Stephen Gemmell, the Scotland sevens coach who has been required to inspire a squad largely selected by his predecessor, Phil Greening, and which under-performed earlier in the season. Gemmell is well aware that little separates the eight countries in the qualifying competition. "All of the sides are capable of beating each other and they're all coming to London with the same sense of desperation," he said.

On the positive side, Scotland had wins over both Spain and Portugal last weekend, although both Iberian sides have posted good results earlier this season. Worryingly, Scotland lost to Tonga in the Australia leg of the World Series and will have to contend with a Hong Kong team that beat Argentina and South Africa in their own tournament.

Scotland have an early start today against a little-known Georgia side at 9.22am, before taking on Zimbabwe at 12.34pm and Hong Kong at 4pm. The eight sides are divided into two pools of four and will be ranked 1-8 at the end of today's play. In tomorrow's quarter-finals it will be 1 v 8, 2 v 7, 3 v 6 and 4 v 5.

Gemmell believes that today's pool stage is all about preparing for tomorrow. "Saturday is about gaining momentum, but we need to win our quarter-final and, for that, we have to play with tempo and apply more pressure at the breakdown," he said.

James Fleming, the experienced sevens winger, has joined the Scotland squad in London in place of the injured John Houston. Fleming, who began his career with Perthshire and has played for Dundee HSFP, has been a prolific try scorer for Scotland sevens and will add another dimension to their attack at Twickenham.

HSBC Sevens World Series Qualifying Tournament, Twickenham, today & tomorrow

DRAW. Pool 1 Scotland, Hong Kong, Zimbabwe, Georgia

Pool 2 Portugal, Spain, Tonga, Russia

Squad. Scotland 7s (Scotland 7s-contracted unless stated) Chris Dean (Scotland 7s EDP), Struan Dewar, Michael Fedo, Alex Glashan (Scotland 7s EDP), Colin Gregor (capt), James Fleming, Lee Jones (Edinburgh), Michael Maltman, Byron McGuigan (Glasgow Warriors), Scott Riddell, Colin Shaw, Andrew Turnbull