He showed himself to be one of the most versatile of the Norwich School of painters: although the great majority of his works were still lifes and landscapes, he was also a drawing master and a miniaturist.

[6] It held regular exhibitions at Sir Benjamin Wrenches Court and elsewhere, and had an organised structure, showing works annually until 1825 and again from 1828 until its dissolution in 1833.

After completing his education, Sillett worked in the city as an apprentice to a heraldic painter,[12] and so his artistic career began in a similar way to those of his contemporaries Crome and John Ninham.

[24] He became a good miniaturist, although G. C. Williamson in The History of Portrait Miniatures (1904) barely mentioned him, but noted that "his really notable work (was) scene painting, which he did for both Drury Lane and Covent Garden theatres".

[27] He painted game, fruit and flowers with considerable skill, often illustrating plants with a suggestion of the existence of a shadow, to give them a more three-dimensional appearance.

[31] Whilst in London it is thought that he was involved in painting scenery at Drury Lane and Royal Italian Opera at Covent Garden, along with the Norwich artist William Capon.

[32] In 1804 he moved to King's Lynn to be closer to his wife's relatives, advertising as "Professor of Painting, Oil and Water Colours, and Drawing Master".

[37] In a barely concealed dig at John Crome (and thus at the old Society), Sillett wrote, "There is more beauty in the delineation of flowers from the garden and human figure rather than pig stys [sic] and cart sheds ..."[15] Along with other members of the group, he showed his works at its exhibitions for three years before it was disbanded.

[15] Although highly regarded as a painter during his life time, rivalry between local drawing masters caused him to write to the Norwich Mercury in 1817, in order to emphasise that his teaching "is by no means confined to Fruit, Flowers, &, as has been intimated".

[30] In 1826 he published his own Grammar to Flower Painting; : being a concise, plain, and easy method for amateurs to attain the rudiments of the science without the help of a master.

[41] The engravings, which almost definitely were produced in response to Ladbrooke's Views of the Churches of Norfolk,[34] accurately depict the important buildings of Norwich.

[29][24] He was buried in the Rosary Cemetery, a short distance from the city: an artist's palette can be seen at the top of his headstone .. His obituary was published in the Norfolk Chronicle.

According to the art historian Josephine Walpole, some experts rank him with William Jackson Hooker, an artist who was able to combine accuracy with charm.

[36] Walpole, who finds his watercolours more appealing than his monochrome topographical studies of churches, has noted that his landscapes are usually rather small in size.

Sillett's still lifes, which were produced in both watercolour and oil, are praised by Walpole for being highly finished although stylistic, with large carefully depicted flower heads placed in characteristically small vases.

According to Walpole, his 1803 watercolour Garden Mallows, now kept in the British Museum, skilfully achieved the desired effect of showing petals that are both strongly coloured and virtually transparent.

[15] He described Sillett's early landscapes as characteristically primitive and displaying "a delightful ability to handle paint", noting his mastery of tone and the beautifully depicted skies in his moonlit scenes.

Day compared Sillett's copper engravings and depictions of figures with those of John Crome, whose influence is discernible, as well as reserving praise for his paintings of flowers, describing them as being "of good colour, carefully drawn and well composed".

[36] His works now sell in his home country and in the United States for high prices: with his oil painting Auricula Primrose fetching £32,200 at auction in 1996.

His 1830 Still-life with Peaches, Apples, Grapes, Plums, Cherries and Gooseberries in a Dish with Hazelnuts and a Snail on a Ledge (54 x 66.3 cm), which was sold in London in 1993, fetched £8,625.