Coordinates: 51°49′52″N 0°12′54″W / 51.831°N 0.215°W / 51.831; -0.215

Welwyn ( /ˈwɛlɪn/) is a village and civil parish in Hertfordshire, England. The parish also includes the villages of Digswell and Oaklands. It is sometimes called Old Welwyn to distinguish it from the newer settlement of Welwyn Garden City, about a mile to the south.

Situated in the valley of the River Mimram, Welwyn was first settled in the Iron Age^{[citation needed]}. The Belgae colonised the area in the 1st century BC^{[citation needed]} (although the Catuvellauni are more often associated with this area) and later it was settled by the Romans. Many Roman artifacts have been found, and the remains of a Roman bath house may be visited. Much later, in the 17th century, as it lies on the old Great North Road, it became an important staging post and a number of coaching inns remain as public houses. After the Great Northern Railway by-passed the village due to the objections of local landowners, Welwyn became less important. Having previously been seen as a town on par with Hatfield and Stevenage, it gradually was seen as a village. The 20th century brought major expansion to the area, as estates to the south, west and north of the village were built up.

The British Rail Class 31 diesel locomotives, also known as the Brush Type 2 and originally as Class 30, were built by Brush Traction from 1957-62.

The Class 31 was one of the Pilot Scheme locomotives ordered by British Railways to replace steam traction. They were originally built with Mirrlees JVS12T 1,250 bhp (930 kW) and 1,365 bhp (1,018 kW) engines and Brush electrical equipment, but the engines were not successful and in 1964 a programme of works commenced to re-engine the fleet with the 1,470 bhp (1,100 kW) English Electric 12SVT engines. The locomotives were originally known as Class 30 under TOPS, with re-engined examples joining Class 31. The class was originally intended for service on the Eastern Region, but gradually became common in both the Western and London Midland regions too.

Several sub-classes of Class 31 exist:

These first 20 locos, originally numbered D5500-D5519, were always easily recognisable as they did not have the headcode box mounted on the roof above the cab, leading to the nickname "Skinheads". They were also nicknamed "Toffee Apples" from the shape of the control key which had to be taken from cab to cab when changing ends. These pilot scheme locos were non-standard in having Electro-Magnetic Multiple-Working control equipment, and were limited to 80 mph (130 km/h). The Class 31/0s had a Route Availability of 5. After being involved in a serious collision D5518 was rebuilt as a standard loco with indicator boxes, blue star coupling code and 90 mph gearing.