Louisa Michell, second daughter and co-heiress of Richard Michell of Culham Court, Berks, and North Audley Street, London, and of Broomfield House, Middx.
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In a research produced by Culleton for RCLPL in 1912, it says:

Richard Michell: b. 1728, died 1789.  In marr lic 1789 [sic] described as of the parish of St George’s, Hanover Square, a bachelor & aged above 30.  Died 11 May 1789 in North Audley Street; intestate.  Letters of administration granted 26 May 1789, described as of Culham, co. Berks, a widower.
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Michell Arms:
Per Chevron gules and sable, a chevron argent, guttee-de-larmes between three swans of the third (within a bordure or).

The bordure may only have been used by the cadet Michells of Forcett Hall, Yorks.

Crest:
Upon a mount vert a swan proper guttee-de-larmes and in the beak a trefoil slipped azure.

Motto
Utile quod honestum

Per Chevron gules and sable, a chevron argent, between three swans of the third.

Burke’s LG of 1914, p. 1314, JCC’s Mrs P L Powys’ diaries and the bookplates of General George Michell.

Their marriage, transcript by me, from an image of the Register, thanks to Ancestry:

[                     [Register of ]  St George, Hanover Sq > 1760-1768             ]

“                 Marriages in July 1763                             231

“No 295
“Richard Michell Esqre of this Parish, Batchelor, & Charlotte Dunbar of St James’s Westminster, spinster, were married in this church by Licence of the Bishop of London this twenty-first Day of July in the Year One Thousand Seven Hundred & Sixty three by me, S Initon, Vicar of Rydge
This Marriage was Solemnized between us,  Rich’d. Michell,  Char’te. Dunbar
In the Presence of,  Thos. Tash,  Eliz Agnew.
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Note that at Charlotte’s marriage one of the witnesses was Eliz Agnew.

Then ask  yourself if this marriage below might just have been that of the mother of Charlotte?

First name(s)           Elizabeth
Last name               Dunbar
Marriage year           1750
Marriage date           06 Sep 1750
Marriage place          London
Spouse's first name(s)  Andrew
Spouse's last name      Agnew
County                  London
Country                 England
Record set              England Marriages 1538-1973
Category                Birth, Marriage, Death & Parish Records
Subcategory             Parish Marriages
Collections from        England, Great Britain

But it says in the register page that she was a spinster, which would not have been true for Charlotte’s mother who might have been a widow.
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