Other members of Team Millennium include press and communications officer, Laura Wilby, event manager Marc Davies, sponsorship and branding executive Huw Lock, ticketing manager James Cummings, Women's Welsh Rugby Union national academy co-ordinator Sophie Bennett, debentures manager Nigel Saunders, commercial and sponsorship manager Craig Maxwell, and venue sales assistant Carrie Phillips.
Sergeant said: "This will be the third year the Cardiff Marathon and Half Marathon have finished inside the Millennium Stadium so we thought it was time we joined in the fun and entered a team to run.
"We're all fairly sporty, although Jilly is the only one of us who is an experienced long-distance runner, having completed the London Marathon. For the rest of us, taking part in the Cardiff Half Marathon will be a totally new sporting challenge."
The team began training in earnest this week - under the watchful eye of Welsh Rugby Union fitness coach Mark Bennett, who has written a training programme for the runners which includes using areas of the stadium for improving their fitness.
The runners have also been placed on a special three-month eating plan by WRU nutritionist Dan King.
Team Millennium will be raising money on their half marathon run for The Toby Lloyd Cockbain Foundation, a charity to support children with cancer, founded by Wales rugby international Brent Cockbain and his wife Kate following the death of their one-year-old son Toby.
Cardiff Marathon organiser Jean Summerhayes, of Barnardo's Cymru, said: "The Millennium Stadium has been an integral part of the marathon and half-marathon event for the last two years.
"We know from messages we receive that for many of the runners the opportunity of being able to finish with a lap inside the stadium is one of the highlights of the event. We are delighted that the venue will be playing an even more active role this year and we wish the team luck."
More than 4,500 runners have already signed up to run the 2006 Cardiff Marathon and Half Marathon on Sunday, October 15 - and it's not too late to join them to help raise money for the charity or good cause of your choice.
The event includes a city centre start with a fast and flat course taking in Cardiff Bay, across the Barrage, around the residential streets of Grangetown and Riverside, through the parkland of Pontcanna and Bute Park, into the grounds of Cardiff Castle and finishing with that lap inside the Millennium Stadium.
You can sign up to join either the Cardiff Marathon or Half Marathon by filling in an entry form via the Cardiff Marathon website at www.cardiffmarathon.org or by ringing the Marathon Hotline on 0870 428 6102.
Organised by the Barnardo's Cymru children's charity in conjunction with Cardiff Council and the South Wales Echo, the Cardiff Marathon is open to anyone aged 18 and over on or before race day. Half marathon runners need to be 17.