Was there any English Commander-in-Chief named Stephenson in the Battle of Agincourt ?

Answer 1

Henry the V, addressing his men on St Crispins Day, the day of Agincourt:

........ But we in it shall be remembered-
We few, we happy few, we band of brothers;
For he to-day that sheds his blood with me
Shall be my brother; be he ne'er so vile,
This day shall gentle his condition;
And gentlemen in England now-a-bed
Shall think themselves accurs'd they were not here,
And hold their manhoods cheap whiles any speaks
That fought with us upon Saint Crispin's day.

or so says W. Shakespear

Answer 2

The commander of English forces was King Henry V (Lancaster).