GWR C/I Signal Box Board NORTH'S COLLIERIES SIGNAL BOX. Next box to Maesteg Neath Road, measures 102 in length. Note: North's Navigation Collieries was the major colliery company in the Maesteg (Llynfi Valley) district. The company owned three large collieries in the Valley: Caerau, Coegnant, and St John's (locally known as Cwmdu Colliery). The company's internal railway system connected the collieries to the G.W. and Port Talbot railways and North's also had running powers over the G.W. and PT track via Cwmdu Sidings.