Callowland is the club's first venture into P4 standards and is the culmination of a challenge to build a layout portraying the 1990s at Scaleforum, and return it in the millennium year as a working layout.
Callowland is the former name of the area now known as North Watford. The layout depicts a small part of the ex- L&NWR St. Albans branch (Watford Junction to St. Albans Abbey) between the north end of Watford North station (the end of the platform can just be seen beyond the level crossing on the layout) and the bridge over the line carrying the A41 trunk road, as it might have appeared had the sidings remained in use into the 1990s.
The main line leaves Watford North station over Bushey Mill Lane on the level and immediately passes the sidings serving the industries alongside before disappearing under the A41 bridge towards Garston, Bricket Wood, Park Street and St. Albans Abbey (Although a terminus, it was once a junction with the GNR branch from Hatfield). The sidings feed to a single line through the bridge acting as a headshunt for the Cow Lane coal yards (unseen on the layout).