Michael: I read your posting with interest . My ancestor was Lt.William Meacham (aka Mecham), the Paymaster referred to. He was in the 28th from c1756, first as an NCO, then commissioned QM/Paymaster 1775, Lt.1779. Meacham died Limerick 1791, probably thyphus. He would have served under Cathcart for many years and so admired him that he named his second son John Cathcart Meacham (b.c1779). His first son he named William Prescott Meacham (b.c1777) after Col.Prescott, who led the regiment. Both the Paymasters sons later served in the 28th. The eldest, as Major Wm.Prescott Meacham, was killed at Waterloo, and Major John Cathcart Meacham transferred to the 24th and died 1828.
The 28th was really a family affair: QM/Paymaster Meacham also had 4 daughters and it seems some of those married 28th Foot officers; Martha m.Capt Wm.Forster Dalton in 1793,'Miss' Meacham m. Capt.William Irving (later Col. of 13th F)in 1803. Of the other two, Sarah married Patrick halpin Hamilton (no info)and Jane m.John Culloden (no info).
Question: Do you have any more info on the Paymaster from the diary? The payment made for John Cathcart's funeral was some time after his death, I note.