When researching No 1 Armoured Train Royal Garrison Artillery , information from Wigeon revealed that the unit was re-designated 523 Siege Battery and the armoured train broken up. The 523rd would re-equip with 9.2 inch Mark XIII railway guns. Thanks to Paul aka Ororkep who posted a photograph of one of 523 Battery's guns, it raised an interest in what the Battery did in the closing months of World War One.

523 Seige Battery was formed on 17th January 1918 being a unit re-designation of No1 Armoured Train RGA. The Battery was formed pending the disestablishment of the armoured train and re-equipment with two 9.2 inch Mark XIII railway guns (range 20,700 metres - 22,000 yards - 12.8 miles).

On the 16th January the armoured trains locomotive and Royal Engineer personnel were returned to the Railway Operating Department. Over the next two weeks the remaining 6 inch gun, rolling stock and guns stores were withdrawn.

The unit came under the command of 26 Brigade RGA (HAG)  and personnel underwent instruction on a 9.2 inch railway gun with 461 Siege Battery at Treizennes (20km NW of Bethune).  On 5th March 523 SB transfered to 55 Brigade RGA (HAG), with the 523rd's first action being recorded on 13th March. At the beginning of April the Battery was transfered back to 26 Brigade RGA (HAG) supporting First Army.

Operating around Lens the shoots over the six months to September were mainly interdiction targets, mostly railways and railway stations.

In September 1918,  26 Brigade RGA (HAG) took over a 9.2in  Mark XIII with limited life, and manpower was drawn from 523 Seige Battery and 461 Siege Battery to operate the gun. September saw 523 SB firing most days conducting interdiction missions, counter battery shoots, and firing harassing fires programmes around Douai, Quincy and Flers.   The last mission of 523 Seige Battery was fired at 06:00 2nd October 1915 when 50 rounds were fired on a harassing fires programme.

 As the Allied Armies started to push German forces back during October the  communications and railways that  had previously been targeted  were now required for the advancing armies. On the 22nd October the railway guns of 26 Brigade RGA (HAG) were collated around Arras and all available personnel were employed on constructing telephone routes and railway construction. This work continued  through to December, when time started to be given over to sports and recreation.

On 1st November 1918, 523 Seige Battery is recorded as being located at Sheet 51C F30 which places it in sidings at Fond De Vase (6km NE of Arras)

The handing over of equipment and the demobilisation of personnel  commenced in January 1919.  However, whilst an Armistice was in place, no Peace Treaty had been signed and in February orders were issued for 523 Siege Battery to be transferred to Second Army on the Rhine and brought up to fighting strength. Whilst some Siege Batteries of 26 Brigade RGA (HAG) moved to Germany in April and May 1919, there was no further movement of 523 SB.

The war diary of 26 Brigade RGA (HAG) records for the 28th June 1919 "PEACE SIGNED at 15:12 hours". Two days later guns and stores were ready for despatch and 523 Seige Battery would be disbanded.