Lady Di was a Spencer, arguably a more English family than the Windor's, Prince Charles' family who arived in Britain the the late 19th century from Germany. The Spencer's bear the Escallope on the Bend sable. The Escallope is a symbol of distant travel on behalf of the realm, essentially an award for foriegn diplomacy.
The scallop also appears on the Label on the Arms and the Supporters of Prince William. The Label of three parts signifies William's first-born status as an heir to the British throne. His younger brother, Harry and any other grandchildren except Harry will have a Label of five parts.
According to Chris Puncher, the man who made the application this class has been using, this is the line of succession:
Prince Charles - being the reigning monarch's eldest son
Prince William - Charles' eldest son
Prince Harry - Charles' second son
Prince Andrew - the Queen's second son
Princess Beatrice - Andrew's eldest child
If one reviews these three achievements of the Spencer's and Sir Winston Curchill you can easily see their family relationships. I did not realize their familial relationship until I noticed the
Quarterly Argent and Gules in the 2nd and 3rd Quarters a Fret Or over all on a Bend Sable three Escallops of the First. on Lady Di's and Sir Winston's shields.
In additon to the three Escallopes on Bend sable, 2nd and 3rd quarters, Churchill also has the Knights of the Garter belt surrounding his arms.