I thought you might be interested to see this portrait of Sheriden by Sir Joshua Reynolds, dating from 1788-9.

Sheriden is shown here wearing the unofficial uniform adopted by members of the Whig political party- blue jacket and buff waistcoat. He was of course a political animal, and became a Member of Parliament for Stafford.

He had entered politics on a platform of electral refrom,and by this time was intimate with the two key figures in the Whig party, Edmund Burke and Charles James Fox, whom he got to know through their shared membership of the Literary Club.

During the 1780s Sheriden's stature as a parliamentarian grew streadily owing to his charismatic personality and formidable debating skills.

See Joshua Reynolds: The Creation of Celebrity(2005), catalogue of the Tate Britain exhibit: essay by Mark Postle

He was probably best known in parliamentary terms for his epic speech in the debate for the vote to impeach Warren Hastings in 1787, but that need not concern us here ;-).

As regards this portrait,the sitter was not at all pleased with the end result.:

Sheriden was unimpressed, believing that Reynolds had emphasised certain facial flaws, notably his red, blotchy complexion. So concerned was Sheriden that his physical shortcomings would be replicated in the print being made from the portrait that he made frequent visits to the engraver, John hall. As Hall's pupil remarked, while he could understand a female sitter being worried about such a matter, he was surprised that it should have had the power to ruffle the thought of the great wit, poet and orator of the age
(as above page 162).

Here is another view of Sheriden- from the Voume of The British Theatre edited by Mrs Inchbald which contian his plays. I'll be reporting her comments on The Rivals later :-)