That's a pity.
Anyway, the John Harnwell of the 18th Dragoons died 26 February 1809.
Said to have attested at Norwich in 1805
Age 23 (I think it means he was 23 when he attested)
Born at Bressingham, Norfolk
Occupation Linen weaver
That's from a description book in class WO 25 at TNA, on ancestry! No mention of Long on the army records.
The estate duty register for that 1809 administration granted to his widow Mary can be downloaded for free from TNA (preview it with the watermarked image viewer!)
Abstract of Administration of John Harnwell otherwise Long, Private in the 18th Dragoons
https://discovery.nationalarchives.gov.uk/details/r/D7234312(not working for me at the moment, I doubt it has anything much of any help though)
Possible?
Baptism at Bressingham, 2 Sep 1781, John, son of Lydia Long
Meanwhile, 25 January 1801, Bressingham, Norfolk
John Harnwell
+
Mary Noble
Both single and of the parish. By banns. He signed, she marked.
Baptism of son John at Bressingham in 1802

Then what happened to them?