WRU Participation Officer in Colwyn Bay, Carwyn Lewis, will join his Llanelli colleague Daryl Richards as well as Cardiff and Swansea based Development Officers Matt Silva and Andy Williams to make up the WRU team.
They will also be joined by the only female racer from the WRU, Hospitality Officer Amanda Williams, as they unite with some of the world's greatest runners to tackle the route from Blackheath to Buckingham Palace.
Each running their first marathon, the competitors have embarked on a gruelling training schedule in their rugby communities throughout Wales to prepare for the big event and raise money for Welsh rugby's nominated charity.
Former Wales scrum half Andy Williams and ex-Wales Youth and rugby league international Matthew Silva jumped at the chance to swap their rugby boots for running shoes when the WRU revealed the opportunity for five of their staff to compete in the upcoming marathon.
While training has been tough at times, the former international players said the fantastic support from their colleagues and peers has boosted their efforts and allowed them to raise a significant amount of money for rugby players injured on the field of play.
"Raising money for charitable causes is a massive part of the London Marathon and I am so proud to have the opportunity to represent the WRU on race day while supporting the Welsh rugby players that have been seriously injured on the rugby field," said Silva.
Former Wales, Newport Gwent Dragons and Ospreys player Williams added: "The lives of these individuals have been seriously affected by their injuries and I feel privileged to have the opportunity to run in support of the Welsh Rugby Charitable Trust.
"Training for a marathon can get tough at times but the opportunity to support the Trust is a massive driving force and I'm grateful to all the friends, family and colleagues that have helped to make a significant contribution to fundraising efforts of the WRU team."
With less than one week to go until the big day, WRU Group Chief Executive Roger Lewis, added: "I wish our 2012 runners all the best as they make their final preparations for the 26-mile run on Sunday. They've each given a lot of time and effort to raise money in support of the Welsh Rugby Charitable Trust and I hope that the opportunity to take part in the London Marathon will bring fond memories for years to come."
Anyone can support the WRU team and the Welsh Rugby Charitable Trust via http://uk.virginmoneygiving.com/mattsilva