On Thomas' Police Record it says:
"Wife born at Rodborough. Previous trade or employment Private 90th Regiment of Foot. Army or Naval Reserve?"
So maybe he was at sea?
I was somewhat surprised by the reference to the 90th Regiment of Foot as this was a Scottish Regiment with the full title of 90th Regiment of Foot (Perthshire Volunteers) (Light Infantry). There was a Private Thomas Keene (number 1539) recorded in the 1841 Worldwide Index, where he is shown as being at the 90th Foot Regimental depot in Tralee, Ireland, but I am inclined to think, based on what we know so far, this is not the correct man.
The newspaper article from the Devizes and Wiltshire Gazette dated 7th Dec 1848 (shown above in
posting #4) says that Constable Thomas Keene, had been a constable in the village of Purton for 8 years by the time of the news article, meaning that, unless the article was wrong, he can't also have been in the Army in Ireland in around April to June 1841. However the clincher would be if the register of his marriage in June 1840 showed whether he was still a soldier, or was by then already a policeman.
There is also the question of why, if the 1841 Worldwide Index entry is the correct person, he was in a Scottish Regiment's depot in Ireland if he came from Kent or Wiltshire, and how he came to marry a girl from Kent in 1840. The earliest that he might have joined the Army was 1834 when he was 18, so there was plenty of time for him to do his 5 years' colour service with the regiment (the 90th Foot was then
stationed in Ceylon) and then leave the Army in time to marry in Kent in 1840 and also join the police around the same time and start his job in Purton. This would also accord with the reference in his police record to him being an Army reservist since he would have had 7 years of reserve commitment after completing his 5 years of regular service.
The 1841 British Army Worldwide Index is a modern compilation by Kevin Asplin, created from muster rolls and pay lists between April and June 1841 held by the National Archives and so it is a snapshot in time which roughly corresponds to the 1841 census. The muster rolls were originally compiled on a monthly basis by each regiment or depot and would only include men who were present at the time (so excluding any reservists or those on furlough or detachment). If you were able to get to TNA at Kew it would be possible to check the
muster rolls for the period 1834 -1841 for further traces of Private Thomas Keene 1539. which would show when he enlisted and when he left the Army. Unfortunately there is no easy way of knowing, based on his regimental number alone, when he enlisted.