The group was visiting the common to see the £100,000 Rye Brook river restoration project, which was completed in the summer of 2004 mainly through the work of the common's many volunteers, who gave up 12,000 hours of their time.
Head ranger Paul Ritchie explained to the group that volunteers had built the flow control structure, saying: "The engineer said to them that it was one of the best he has had the pleasure to see."
He highlighted the environmental benefits of projects like these. "It has had an impact because the flash flooding has been improved. However, people need to understand that they are flooding the common and not the other way round."
He said planning should be reviewed so surface water would be adequately drained and not end up flowing directly into streams such as the Rye Brook and cause subsequent flooding elsewhere.
Superintendent Bob Warnock said of the project: "The selection of the engineer was crucial. He showed the volunteers how to do things."
During the visit, Ritchie also highlighted the problems the sector faces with risk management: "We have found ourselves under pressure to cut trees for a horse trail - you can move people, you don't have to cut the trees."
He added that people needed to understand that tree risk management is not just about cutting trees.
In attendance on the trip were Brian Donohoe MP and Baronesses Fookes, Golding and Thomas of Walliswood, alongside representatives from the City of London.