Chris Phillips finally sorted her ancestry:

From: "Chris Phillips" <cgp@medievalgenealogy.org.uk>
Newsgroups: soc.genealogy.medieval
Subject: Maud de Grey, wife of John de Botetourt and Thomas de Harcourt
Date: Wed, 10 Dec 2003 10:58:34 -0000

From our previous discussion in October, it appeared that the account of
Botetourt in the Complete Peerage (ii 235) was wrong in giving Grey wives to
both John de Botetourt, Lord Botetourt (d. 1385), and his son John de
Botetourt (d. 1369). Only the younger John married a Grey - Maud, the
daughter of John de Grey of Rotherfield. But we didn't uncover any decisive
contemporary evidence to determine whether Maud was he daughter of the first
Lord Grey of Rotherfield (d. 1359), by his second wife, Avice Marmion, or of
the second Lord Grey  (d. 1375) - as stated by CP.

We had seen that Maud was commemorated by an "elaborate" tomb at Stanton Harcourt, but hadn't been able to find a detailed description, and according to Pevsner the heraldry on the tomb was modern.

Yesterday I had a chance to look at a small book by George Simon, Earl
Harcourt (d. 1809), entitled "An Account of the Church and Remains of the
Manor House of Stanton Harcourt in the County of Oxford" (1808). This
includes (pp. 8, 9) a description of Maud's tomb, which I've copied below in
case it's of interest to anyone. Genealogically, the important thing is that
four shields of arms are described - Harcourt; Harcourt impaling Grey; Grey;
Marmion.

Further to this, on p. 13 is a description of a monument in the Harcourt
Chapel, to Sir Robert Harcourt (d. 1471) and his wife Margaret (Byron), in
which the heraldry is described as follows:
"On the front, four spread six foils, containing shields with the following
arms; namely, Harcourt impaling Byron twice, and twice Marmion; which Maud
Grey, his grandmother, bore in right of her mother, heiress of the
Marmions."

From the appearance of the Marmion arms on these monuments, it seems clear that Maud was the daughter of John, first Lord Grey of Rotherfield, by his second wife Avice Marmion (and not of his son, John, by his first marriage).

Incidentally, this removes any possible conflict with Rosie Bevan's
suggestion that Maud, wife of Ralph Hastings, could have been a daughter of
the younger John de Grey, as in the light of Maud de Harcourt's parentage
this would not require John to have had two daughters named Maud.

Chris Phillips
_________________________________________________________

Earl Harcourt's description of Maud's monument:
"The ancient monument under an arch in the south wall of the chancel is that
of Maud, daughter of John Lord Grey of Rotherfield, by his second wife,
Avice, daughter and co-heiress of John Lord Marmion, (which Maud, with her
two brothers, assumed the name and arms of Marmion,) wife of Sir Thomas de
Harcourt, son of Sir William and of Johanna, daughter of Richard Lord Grey
of Codnor. She died in the 17th year of Richard II. She has the reticulated
head-dress, with a narrow gold binding across the forehead : a scarlet
mantle lined with ermine, and a deep cape of the same, scolloped at the
edge, on either side of which are two small gold tassels : a broad band of
ermine, with a narrow gold binding across the breasts : the upper part of
the sleeves of the same ; the lower part blue, and reaching to the knuckles,
like mittens. On the surcoat, the arms of Harcourt impaled with those of
Grey. Those parts both of the arms and of the dress which are blue are
damasked. At her feet a small dog. On the front of the monument four
shields, with the following arms ; namely, Harcourt; Harcourt impaling Grey;
Grey; Marmion.