The first fireless locomotive at Thames Mills was 0-4-0 No. 1876 of "Andrew Barclay Sons & Co", this arriving on 14th September 1925. No. 1876 was painted into dark green livery with black lining and became "No. 1" in the mills' fleet list. It was joined by an identical locomotive from the same builder in 1928: this was Andrew Barclay No. 1962, which became the mills' No. 2.
In 1928, production capacity at Thames Mills, Northfleet, was doubled on the commissioning of two more machines. Four years later, Northfleet and Ellesmere Port Mills were reported to have a combined yearly output of up to 250,000 tons of newsprint. The Bowater empire continued to gain momentum through the decade with the aforementioned acquisitions of Sittingbourne and Kemsley Mills in 1936, and the purchase of mills in Newfoundland in 1938. However, after the outbreak of war in 1939, Thames Mills were taken over by the government and ceased to produce newsprint. Thereafter, they were used to manufacture munitions, for which the mills' repair shops were enlarged. At the time, Eric Bowater was appointed as the Director General of Aircraft Distribution, for which he was knighted in 1944.
Manufacturing of munitions at Thames Mills ceased in early summer 1945 and, by the end of the year, newsprint was again being produced. Supplies of pulpwood resumed from Canada and Scandinavia, these being unloaded from ships onto the deep water jetty on the Thames. From there, the raw material was conveyed to the mills upon the internal railway system. This was followed in 1957 by the expansion of both Northfleet and Mersey sites, to boost annual newsprint production of both mills from 225,000 to 525,000 tons. As part of this project, two newly-built diesel locomotives arrived at Northfleet, both having been manufactured by "Ruston & Hornsby" of Lincoln:
No. 416209 became Thames Mills' "No. 3", Nos. 1 and 2 already being occupied by the incumbent fireless steam locomotives. Logic would dictate that No. 412427 became the mills' No. 4, although your author has yet to find reference to this.
In 1960, the single-track linking Thames Mills with the Gravesend West branch was diverted. It assumed a course further to the west, in order to accommodate the coal stacking area of Northfleet Power Station, the latter of which was then being built. The power station was commissioned in 1963 on the former site of Red Lion Cement Works, which had closed as long ago as 1919. The works' redundant chalk pit was used for the power station's ash disposal area, this extending to 32 acres.
As of 1967, Thames Mills had an output of 150,000 tons of newsprint and paper per annum, and the complex covered an area nearing 50 acres. However, three years later, there was a marked decline in the tonnage of newsprint produced, combined with higher average prices for pulp. These factors led to the Bowater Corp announcing, in 1972, the closure of Thames Mills, which at that time had 700 employees. Production was to be moved to Kemsley Mills, Sittingbourne, along with a large proportion of Northfleet's staff, allowing the company to focus manufacturing activities at a smaller nucleus of premises. Closure of Thames Mills occurred in 1973, Bowater-Scott purchasing the entire site. Bowater-Scott had been created in 1956 and the company was jointly owned by Bowater Corp. Ltd and the Scott Paper Company, USA. In its first year, the company established a tissue-producing mill at Northfleet, for which three machines were commissioned. Tonnage was 550 weekly and the mill cost $12,000,000 to build.
Of the four railway locomotives which worked at Northfleet, two survive today. The fleet initially passed into Bowater-Scott ownership after this company's purchase of the redundant Thames Mills in 1973. They eventually came under the "Northfleet Terminals Limited" (NTL) umbrella, a subsidiary company set-up by Bowater-Scott in 1979 to specialise in the handling and storage of imported pulp, timber, and paper. In that year, the company transferred Andrew Barclay fireless locomotive No. 1 to the "Sittingbourne & Kemsley Light Railway Society". The latter, originally a branch of the Locomotive Club of Great Britain, had taken charge of the narrow gauge railway system at the Sittingbourne and Kemsley Mills in 1969, after it was decommissioned by Bowater Corp. Of course, the fireless locomotive was not of the same gauge as this system, so could only be stored as a static exhibit. Then, in 1981, diesel shunter Class 88DS No. 412427 was donated by NTL to the fledging "North Downs Steam Railway", which at that time occupied the former Higham station goods yard under licence from British Rail. The shunter followed the railway to subsequent bases at Chatham Dockyard, Stone (Dartford), and Tunbridge Wells, before finally moving to Oswestry, Shropshire, in 2007, for use on the Cambrian Railway.