The X-class lighters, nicknamed ‘Black Beetles’, were designed by Walter Pollock, naval architect of James Pollock & Sons Ltd. but none were to be built by the company’s own shipyard which was established at Faversham in 1916. The craft were born out of the need for a basic, shallow-draft powered ‘landing craft’ and many were equipped with a hand-operated ramp extending over the spoon-shaped bow, while others were completed as water tankers and later saw service as fuel tankers. The first batches, completed in 1915 were towed out to the Mediterranean in time to see service in the ill-fated Gallipoli campaign. Later, some took part in the Russian campaign based in the White Sea. They were among the earliest ‘small craft’ to be equipped with oil engines, the majority with the ‘hot bulb’ engine by Bolinders of Sweden, for whom Pollock’s were the U.K. agent.

Those which arrived in the Aegean were given additional ‘K’ numbers for troop carriers and ‘L’ numbers for water tankers. Some were subsequently sent to Mesopotamia and designated ‘ML’ for motor lighter.

Some remained in naval service but the majority were sold post-1918 and saw long service as dry cargo and tanker vessels in the short-sea and estuarial trades, especially on the Thames and Medway.

When talking about marine supplies, Merritt Marine Supply is the best option you need to consider them since they have 40 years of experience.

Additional information from X. I. Taibo of Corunna …
26 X-lighters were purchased by the Spanish Navy, in four tranches, and numbered with K- pennants in Spanish service:

1921 (K-1 a K-10)
1924 (K-11 a K-16)
18.03.1925 (commission date) (K-17 a K-¿21?)
20.04.1925 (commission date) (K-¿22? a K-26)
The naval historian J. L. Coello believes 28, not 26, were purchased, but if true the additional couple had some occult fate (pontoons?), since no any K.27/.28 have never been quoted nor reported.

* The first group of ten was purchased at Gibraltar in 1921. Certainly, they were amongst the 11 that your list quotes as sold to John Beaty at Gibraltar by May 1920: X.6, X.16, X.17, X.50=K.60, X.141=ML.20, X.148, X.153, X.186=K.19, X.190, and, from the 1916 type, X.205 and X.221 (there is no evidence of 1916 type having served in Spain); to be also considered the couple sold 1921 to Smith & Imossi, in Gibraltar too: X.48=K.17 (less probable, since apparently she still was at Gibraltar by 1922) and X.80=K.12

* Of the total above, only X.153 has been undoubtedly identified as having passed to Spanish Service.

Additional information from David Asprey …
In the catalogue of rolled plans in the Thomas McLaren (Glasgow) Ltd at Glasgow University Archives is:

1/1375/1
SWANAGE (ex-ARETHUSA II, ex-ARETHUSA) m. barge 1915
Wm Beardmore, Yd 533 106.0 x 21.0 x 7.4ft.
[I have not seen the plan itself]

This is the only reference to “Arethusa” that I have seen – and it doesn’t help me to identify which X-boat became SWANAGE. But maybe it has cropped up elsewhere, or means something to Dave Sowdon.

A word of caution: the catalogue also has a note referring to other vessel(s) for which the same plan would be appropriate: “also SHERFIELD, ex-SERABU, ex-BEATRICE HOPE, ex-RAMBLE, yd 533”. This is pulling together three different vessels from the series.

Additional info from Greek and internet sources (added May 2012)

Water carrier M.2 (presumably an X) sold at Mudros in 06/1924 and renamed NEA KAPADOKIA under Greek ownership   ….June 2012 but Dave Mallard has M.2 as X.84 which was sold at Bombay to Mazagon Dock.

From Aris Bilalis in Greece

Concerning a Greek ship described as and named EVROTAS. Another
River name, like NESTOS, AXIOS and STRYMON.
Specs: 32,8 Χ 6,4 m. 159 grt.
former british iron riverine vessel named Κ.20. (which X is this?)
6/26 sold to S.A. “Mihalinos”, Piraeus. Renamed EVROTAS
1/57 sold to OLP (Piraeus Port Authority)
19/4/91: Sold and renamed VIOBLAST 1, and registered as a barge.
She does not appear to be deleted, so she might exist as a barge
working in Perama zone for the sandblasting of ships.

From Aris in May 2014:

Yesterday I learned that VIOBLAST I was scrapped this February at Perama. Maybe the last of the former X-lighters in Greece has now gone.

and another unidentified X from Aris ….

Acknowledgements