What Is A Famous Battle That England Was Involved In, In The Medieval Days?

Agincourt. Henry V's finest moment. An Army wracked with dysentery, possibly Typhoid, take on the French on their ground.  Through the use of a good defensive position sited on the top of a shallow forward slope, the Long Bow (early Artillery), and using poor weather and ground conditions (rain and sodden ground at the foot of a forward slope, which hampered French Heavy horse). The English beat early cavalry charges, before leaving their DEFILED positions to carry out an ENFILAD, something the French as the attacking force could not do.

Also, the battle of hastings in 1066.