The position is approximate but it makes sense for a steam power house to be close to the chimney.
This is a Belliss & Morcom inverted vertical compound enclosed engine, named Nicholas and installed in 1951. It is serial No. 10566 and generated 362 bhp at 428 rpm driving a three phase alternator. The engine was in regular use until 1978, on standby into the 1980s and was removed for private preservation in about 2002. It is, as far as I know, still in store. The powerhouse also contained an earlier Belliss & Morcom driving a dynamo and that has been removed by a different private collector. The factory still contains a preserved horizontal tandem compound steam engine.