After the death of his first wife, diplomat Sir Henry Francis Howard married 2ndly, 30 August 1841 at Berlin, a lady of the Brandenburg-Prussian nobility, Maria Ernestine von Schulenberg. Sir Henry Francis Howard's entry in Who Was Who says Maria Ernestine had the title of Baroness, but neither the BP article, nor Leo's website, give her that title. Her father Leopold Wilhelm von der Schulenburg was an officer in the Prussian Army and made his seat at Gut Priemern, in Bretsch, Germany, and it was in that house that Maria Ernestine was born:
http://de.wikipedia.org/wiki/Leopold_Wilhelm_von_der_Schulenburg#mediaviewer/File:Gut_Priemern_Sammlung_Duncker.jpg
Leo has all 4 of Maria Ernestine's grandparents in his database, and as none of the four families appear to have any Edward I lines behind them, I haven't traced Maria Ernestine's ancestry back any further.
http://www.genealogics.org/pedigree.php?personID=I00116304&tree=LEO
Sir Henry Howard of the Strand (1843-1921), the elder son of Sir Henry Francis Howard and Maria Ernestine von der Schulenburg, followed his father into the Diplomatic Service, his first posting being to Washington, DC, where he served from 1865 to 1874. It was there that he met his wife, Cecilia Dowdall Riggs (born 20 June 1844 at Washington, DC; died 3 December 1907 at The Hague, Netherlands).
Cecilia's father was the acclaimed banker George Washington Riggs (born 4 July 1813 at Georgetown, DC; died 24 August 1881 at Green Hill, Montgomery County, Maryland), who has a bio in American National Biography (1999). He married 23 June 1840 at Madison, New Jersey, Janet Madeleine Cecilia Shedden (born 20 August 1815 at Newark, New Jersey; died 14 October 1871 at Westminster, London), the daughter of a Scottish merchant who emigrated from Glasgow to Newark.
http://exhibits.library.gwu.edu/pnc_riggs/corcoran_riggs_gw.html
Through her mother, Cecilia Riggs, Lady Howard has a single 18-generation line of descent from Edward III, through Cardinal Beaufort's bastard daughter Jane Stradling. Leo already has it in his database.
Edward III had a son
1) John of Gaunt, 1st Duke of Lancaster (1340-1399) m. 3) Katherine Roet (c.1350-1403), and had
2) Cardinal Henry Beaufort (1375-1447) = unknown mistress, and had
3) Jane Beaufort, illegit. (c.1402-1479) m. Sir Edward Stradling of St Donats Castle (c.1389-1453), and had
4) Sir Henry Stradling of St Donats Castle (c.1423-1476) m. Elizabeth ap Thomas, and had
5) Thomas Stradling of St Donats Castle (c.1454-1480) m. Jennet Matthew (d. 1485), and had
6) Siân Stradling (b. c.1480) m. Sir William Griffith of Penrhyn (c.1480-1531, descended from Edward I), and had
7) Sir Edward Griffith of Port Penrhyn (1511-1540) m. Jane Puleston, and had
8) Ellen Griffith (d. 1573) m. Sir Nicholas Bagnall of Newry Castle (c.1510-1591), and had
9) Frances Bagnall m. Oliver Plunkett, 4th Baron Louth (d. 1607, descended from Edward I), and had
10) Matthew Plunkett, 5th Baron Louth (d. 1629) m. Mary Fitzwilliam (d. by 1661, descended from Edward I), and had
11) Hon. Margaret Plunkett (d. 1683) m. Sir Christopher Aylmer, 1st Baronet of Balrath (c.1620-1671, descended from Edward I)*, and had
12) Catherine Aylmer (d. 1726) m. 2) Capt. Michael Warren of Warrenstown House (d. 1712), and had
13) Anne Warren (1692-1744) m. Christopher Johnson of Smithstown House (1687-1764), and had
14) John Johnson of Warrenstown House (d. by 1808) m. Catherine Nangle, and had
15) Anne Johnson m. Walter Dowdall of Dublin (d. aft. 1800)**, and had
16) Matilda Cecilia Dowdall (1781-1855) m. Thomas William Shedden of Newark (1781-1816), and had
17) Jane Madeleine Cecilia Shedden (1815-1871) m. George Washington Riggs of Green Hill (1813-1881), and had
18) Cecilia Dowdall Riggs (1844-1907) m. Sir Henry Howard
*Gary Boyd Roberts in RD600, pp. 273-275, shows the descent of Sir Christopher Aylmer, 1st Baronet, from Edward I thru the Aylmers. This Edward III descent of his wife Margaret Plunkett is an addition to RD600.
**Very little can be found online about this Walter Dowdall. The only source given for Dowdall in RD600 is 'The Families of Warren and Johnson of Warrenstown, County Meath' (1950) by Franz V. Recum (a descendant of Sir Henry Howard & Cecilia Riggs). I haven't yet seen this source. Walter Dowdall appears to have lived in both Dublin and Warrenstown House, his wife's family home. He had at least three children: 1) Katherine Dowdall m. Thomas Errington of Clints Hall, Richmond, Yorkshire (parents of Archbishop George Errington); 2) Capt. George Robert Dowdall of Stratford, Connecticut (1782-1829), who had a daughter named Ann Johnson Dowdall; and 3) (Matilda) Cecilia Dowdall, maternal grandmother of Cecilia Riggs, Lady Howard. At some point in the 1790s, after his wife had died, Walter Dowdall left Ireland and went to America. He's most likely the Walter Dowdall living in New York in the 1800 census with 1 young adult male & 1 young adult female (his son George & daughter Cecilia, presumably). Cecilia Dowdall married Thomas Shedden in 1806 in Newark, New Jersey, but whether her father Walter was still alive and had moved there from New York, is not known.
If anyone has any further information on Walter Dowdall, I'd be very interested.
Cheers, ----Brad