It’s a hard glaze, right?

Early 20th century Doulton Lambeth stoneware figure by George Tinworth, the seated boy playfully kicking a tambourine. Sold for £480. Photograph: The Canterbury Auction Galleries joined the business aged 15 and, with Watts retiring in 1854, the firm, by now one of the largest in London, restyled itself as Doulton & Co, opening factories in Dudley in the West Midlands and St Helens, Merseyside, to cope with demand.

Henry was an innovator. He introduced steam power to the industry and in the 1850s, recognising the potential of saltglazed stoneware as a medium in the growing appeal of art pottery, he became a mentor and patron to the nearby Lambeth School of Art, founded in 1854.

In the 1860s, he commissioned the students to design and make a frieze for his factory’s new extension, now in the Victoria & Albert Museum, and encouraged them to produce experimental decorative pieces shown at both the Paris Exhibition and the Great Exhibition in 1851.

By 1871, he had launched an art pottery studio at Lambeth, offering design work to students such as Arthur Barlow and his sisters Florence and Hannah, Frank Butler, Mark Marshall, Eliza Simmance, and George Tinworth – all names that excite today’s collectors.

Doulton never looked back. It acquired a factory in Nile Street Burslem, in the Staffordshire Potteries in 1878 where fancy bone china and its famous line of figures and character jugs were produced.

The firm became Royal Doulton in 1901 when it was given the Royal Warrant following a visit by Edward VII and Queen Mary. It continues today, but under much-reduced circumstances following the tough times for the pottery industry at the turn of the current century.

Mark Marshall (1842-1913) followed in his stonemason father’s footsteps, working in a local yard after training at Lambeth School of Art, where he probably met fellow student Robert Wallace Martin (of “Wally bird” fame).

Mark’s first love was pottery, however, and he is known to have assisted Robert Martin and his brothers who made their name producing gothic revival stoneware art pottery, which collectors know today as Martinware.

The brothers’ “Wally bird” tobacco jars modelled as grotesque crow-like creatures fetch eye-watering prices.

Another fellow Lambeth student George Tinworth (1843-1913) was undoubtedly a further influence. A greengrocer’s son, he also worked in Doulton art pottery studio and is known for his amusing stoneware studies of mice and frogs in human activities, he called them “humoresques”, as well as more serious public fountains, friezes, pulpits and other ecclesiastical commissions and memorials.

Buying and collecting pieces by Marshall, the Martin brothers and Tinworth today requires drainpipedeep pockets.