Earl of Cambridge
The three ringleaders of the plot were Edmund Mortimer's brother-in-law, Richard of Conisburgh, 3rd Earl of Cambridge; Henry Scrope, 3rd Baron Scrope of Masham (whose uncle Richard le Scrope had been executed for his part in a 1405 revolt); and Sir Thomas Grey, whose son, Thomas, had been betrothed in 1412 to Cambridge's only daughter, Isabel.