Brad Verity on soc.gen.med on 15th April 2007 has produced a descent to him from Joan Beaufort, countess of Westmorland:

Joan Beaufort, Countess of Westmorland (c.1379-1440) had 2 sons (B1 &
D1) and two daughters (A1 & E1):

A1) Eleanor Nevill, Countess of Northumberland (d. 1473), who had
A2) Henry Percy, 3rd Earl of Northumberland (1421-1461), who had
A3) Henry Percy, 4th Earl of Northumberland (1449-1489) m. 1472 Maud
Herbert, and had
A4) Henry Percy, 5th Earl of Northumberland (1478-1527) m. c. 1490
Katherine Spencer (1477-1542, descended from Edward III but not thru
Joan Beaufort), and had
A5) Sir Thomas Percy (c.1505-1537) m. c.1525 Eleanor Harbottle (c.
1510-1567), and had
A6) Mary Percy (1531-1598) m. c.1550 Francis Slingsby of Scriven (c.
1525-1600), and had
A7) Henry Slingsby of Scriven (c.1560-1634) m. c.1580 Frances Vavasour
(d. 1609/11), and had
A8) Mary Slingsby (1582-1662) m. c.1600 Sir Walter Bethell of
Ellerton, Yorks. (d. 1622), and had
A9) William Bethell, 3rd son, rector of Kirkby Overblow, Yorks.
(1616-1685) m. c.1648 Bridget Bourchier (see B9 below), and had
A10) William Bethell of Swindon (in Kirkby) (1650-1699) m. 2) 1688
Elizabeth Brooke (d. 1707), and had
A11) Slingsby Bethell, younger son (1696-1758), merchant, Alderman,
Lord Mayor of London 1755


B1) Richard Nevill, Earl of Salisbury (1400-1460), who had (with C2
below)
B2) Richard Nevill 'The Kingmaker' (1428-1471), who had
B3) Isabel Nevill (1451-1476) m. 1469 George, Duke of Clarence (see E2
below), and had
B4) Margaret 'Plantagenet', Countess of Salisbury (1473-1541) m. c.
1490 Sir Richard Pole (d. 1504) and had
B5) Henry Pole, 1st Baron Montagu (c.1492-1539) m. Jane Nevill (see C5
below), and had
B6) Winifred Pole (d. 1602) m. 2) Sir Thomas Barrington of Barrington
Park, Essex (d. 1586), and had
B7) Catherine Barrington m. 1584 William Bourchier of Beningbrough,
Yorks. (descended from Edward III but not thru Joan Beaufort), and had
B8) Sir John Bourchier of Beningbrough (d. 1660) m. c.1625 Anne Rolfe,
and had
B9) Bridget Bourchier (d. 1662) m. c.1648 Rev. William Bethell (see A9
above)
__________________________________________________________________________________________