The Y1/Y3 sentinel was based on the road going lorry, utilising a similar centrally mounted steam tube boiler and chain drive system to the wheels. Whilst not having the greatest turn of speed (approximately 36mph top speed) these small locos proved capable of pulling a constant draw weight and were considered ideal for shunting in yards and providing motive power along smaller branch lines. These quirky little locos were used by all of the big four railway companies but it was the LNER that used and ordered greatest number. Many Y1s and Y3s were produced and continued to provide service until their phased withdrawal over the 1940s and 1950s. Seven survived into departmental stock until the 1960s. Only two Y1/Y3s survived into preservation in the UK.

The Dapol Sentinel includes the following features:

Die-cast running plate

Die-cast chassis, Die-cast and profiled wheels

High level of separately applied detail

Glowing fire light effect

Removable body to allow easy fitting of crew members

Sprung metal buffers and articulated screw coupling

Dapols proven motor and gearbox offering exceptional smooth performance and slow running capabilities

DCC Ready (21 Pin), DCC Fitted with sound options available