Looking at the muscular frame of the modern sevens rugby player and the sparrow-like physique of the Tour de France rider, you would be right in thinking that rugby and cycling don't go hand in hand.

Which only makes any pedal-powered challenges by rugby players all the more impressive. First Lawrence Dallaglio, a World Cup winner with England in both forms of the game, embarked on a epic bike ride between every Six Nations venue.

And now my son and 11 of his rugby sevens-playing mates are set to take on a stage of the Tour De France, known as the Etape, in aid of the cancer charity set up in my deceased son's name. And it is not just any stage, but the toughest of this year's Tour.

Some 183 lung-bursting kilometres in the scorching heat and rarified air of the Pyrenees await them on July 18. They will climb 4100 metres in vertical height (that's three times the height of Ben Nevis) up gradients of up to 16 per cent on ascents as long as 21km.

It retraces much of the original stage from Pau to Tourmalet in 1910 where Octave Lapize, the first man to reach the final summit, turned to the organisers and screamed: "Vous etes des assassins!" The dozen making up the Etape team will most likely have murderous thoughts too when they reach that final thigh-burning climb.

Joining the pros in the Pyrenees

Far more comfortable spending their summers playing on the sevens circuit for teams such as Jedi and Samurai than in the saddle, the team includes Ed Jennings, formerly of London Broncos and Harlequins, Piers Michell, once of Richmond and Harlequins, Ross Jennings, a former Oxford Blue, my son, a former England schoolboy international and Tim Lacey, formerly of Gloucester and now CEO of UR7s, the organisation that has launched the inaugural National Sevens Series that is set to revolutionise the game in this country.

The majority of Etape entrants will be experienced pros or club cyclists who train all year for their chance to take on this gruelling stage. As few as half will make it - the rest give up or are forced to stop as they fall too far behind. The challenge the guys face is enormous.

But Julian would not have had it any other way. An outstanding rugby player himself and like his brother, a sevens specialist, had Jules been around today he would have no doubt been climbing those hills like an experienced pro but that's the thing with cancer - it has no respect for health, it makes no allowances for fitness, it cares nothing for how much a person enriches other people's lives.

Today, seeing the likes of all-time greats such as Cliff Morgan of Wales and Andy Ripley of England battling against cancer only underlines the cruelty of this disease.

After a brave fight against the T-Cell lymphoma strain of cancer Jules died in May 2001. For my wife, Ros and son, Charles, it was doubly tough as my daughter, Charlotte, died from an unrelated rare blood disorder a decade before. We set up the Julian Starmer-Smith Fund so that other families do not have to go what we have.

Not enough is known about T-cell Lymphoma which affects some 12,000 people in the UK every year. A team of expert scientists in Oxford, led by Chris Hatton, are already making great strides but they need more funding to continue their critical research into this terrible disease.

So it is with delight and gratitude that I can announce that UR7s and the National Sevens Series have chosen to support this cause. The Series represents an exciting new departure for sevens - providing the platform to showcase the mesmerising skills, speed and power of rugby's most exciting form, but also the parties, fun and festival atmosphere that makes Sevens so unique.

So come July 17 while you are witnessing some the greatest sevens players do battle on the sun-kissed fields of Newquay for the climax of the series, spare a thought - and a few quid, if you can - for this brave dozen as they prepare for the greatest race of their life.

To make a donation please visit the Julian Starmer-Smith Fund at www.justgiving.com/jssfund.

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