With assistance from family in the UK (you know who you are!), I sent away for copies of the Smithers articles that I found in the online indexes to ‘The Cambrian’ newspaper. Unfortunately the text contains little more information than that revealed in the index. The entry from 28 January 1809 says:

On the 21st inst. at St Martin’s church, Strand, London, Mr. H. K. Smithers, of the Adelphi, London, to Miss Pitman, of Barnes, Surrey.

This event was not publicised in the London Times, as far as I can tell from the Digital Times archive, so this suggests that the marriage was of more significance to people (i.e. family) in Monmouthshire, rather than London. The second item was from 25 April 1812, included in the “Bankrupts from Tuesday’s Gazette”:

H. and H. K. Smithers and G. Buck, Newport, Monmouthshire, coal-master, April 25, May 12, June 2, at Guildhall; Attornies, Colins and Waller, Spital-square.

I’m presuming that the ‘Gazette’ referred to is the Welsh Gazette, as no bankruptcy notice of this nature appears in the London Gazette for Tuesday 21 April 1812 in the London Gazette online archives. I have previously assumed that this Smithers family originated in and around London, as they appear in London Post Office directories from 1817 onwards. Maybe this is where H. K. Smithers moved to re-establish himself after experiencing financial difficulties in his home of Newport. I need to discover if there are any Smithers birth, marriage, or death events around Newport. I also need to find a copy of the Welsh Gazette for 1812.