The official list of all-party groups lists the contact address for the group as "The Newbridge Partnership" at Cowley House in Little College Street, just round the corner from the House of Parliament. In fact, this is the office of the Citigate Westminster lobbying firm.
The contact for the group is Chris Austin, who now works for the firm but who used to be public affairs manager at British Rail. Its joint chairman, Labour MP Peter Snape, has a number of rail-related interests and its treasurer, the Labour peer Lord Berkeley, is also chairman of the Piggyback Consortium, a group which plans to cut the number of road journeys by transferring freight to rail.
The rail group set up some years ago and then revived after the last election, has 65 peers and MPs on its membership list.
Although only MPs and peers can be members of all-party groups, Mr Austin's support is paid for by the Railway Forum, which has about 40 members with major interests in rail. These include Railtrack and Great North Eastern Railways. The group meets regularly in the House of Commons, and can often boast heavyweight speakers.
As well as hearing Mr Prescott later this month, members will also have the chance to question Railtrack executives about the Channel Tunnel Rail Link before Christmas. Their last meeting was addressed by the Central Railway Group, which wants to build a freight railway between Liverpool and the Channel Tunnel.
Mr Austin says the group is prepared to hear from people with all sorts of different views:
"Some groups have been criticised for keeping out competitors, but we would not do that. In the next three meetings we will have the Deputy Prime Minister, who is above suspicion, we have Railtrack which is a member of the group and we have Stagecoach, which is not. Rail touches everybody at a constituency level."
Mr Snape, Labour MP for West Bromwich East, lists a number of transport links in the Register of Members' Interests. He is chairman of Travel West Midland, and has shares in National Express PLC.
According to the official lobbyists' register covering the first six months of the year, Citigate Westminster also represented British Railways Board, The Railway Industry Association, Virgin Rail, Anglia Railways, Great Western Trains, London Underground Limited, Scotrail and Thames Trains.