Hello Lesley,
'the selfish whotsit' was fairly close to the mutterings I was making while reading the letter (the first two words were the same)
The letter, written in 1885 the year he married his third wife, was written in pencil and still in the original envelope. I couldn't believe it.
Here he is with his second wife and the boys (minus my husband's g grandfather Thomas age 15 who seems to be working on a farm in Stirlingshire).
You would never think from looking at this census what a

he was.
Dwelling: 11 Glebe St
Census Place: Glasgow, Lanark, Scotland
Source: FHL Film 0203648 GRO Ref Volume 644-6 EnumDist 13 Page 7
Marr Age Sex Birthplace
Thos. CAMPBELL M 36 M Hamilton, Lanark, Scotland
Rel: Head
Occ: Tailor
Helen CAMPBELL M 36 F Balfron, Stirling, Scotland
Rel: Wife
John R. CAMPBELL 7 M Glasgow, Lanark, Scotland
Rel: Son
Occ: Scholar
Duncan Mc P. CAMPBELL 6 M Glasgow, Lanark, Scotland
Rel: Son
Occ: Scholar
Alex. R. CAMPBELL 3 M Glasgow, Lanark, Scotland
Rel: Son
Peter CAMPBELL 4 m M Glasgow, Lanark, Scotland
Rel: Son
I've been able to follow the boys (except Peter who wasn't named in the poorhouse application

) through to marriage. I've even found his third wife marrying again and dying in Stirlingshire. I can only assume (there's that word again) they went abroad after marrying and she returned to Scotland after his death.
Any way as you said what a find and I can't believe I haven't found it before.
kind regards,
Annette M