It’s the Feast of St. George, patron saint of England and several other countries, as well as Moscow. He was martyred by Diocletian after extensive torture and miraculously saved the city of Beirut from a fierce dragon. His intercession is especially powerful against Turks and Jihadists.
You might find this prayer helpful:

Faithful servant of God and invincible martyr, Saint George; favored by God with the gift of faith, and inflamed with an ardent love of Christ, thou didst fight valiantly against the dragon of pride, falsehood, and deceit. Neither pain nor torture, sword nor death could part thee from the love of Christ. I fervently implore thee for the sake of this love to help me by thy intercession to overcome the temptations that surround me, and to bear bravely the trials that oppress me, so that I may patiently carry the cross which is placed upon me; and let neither distress nor difficulties separate me from the love of Our Lord Jesus Christ. Valiant champion of the Faith, assist me in the combat against evil, that I may win the crown promised to them that persevere unto the end. Through Christ our Lord, Amen.

The account of his fight with the dragon and the demonic idols of Beirut can be found here.
For St. George and England,