Eingang nach Jerusalem von BL Royal 2 B VII, f. 233v

Miniature of the Entry into Jerusalem with Christ on a donkey's back, two disciples, a boy in a tree and a man laying down a blue cloth, with an historiated initial 'D'(ixit) of the Trinity, containing the Father and the Son holding spheres and the Holy Dove descending down between them, with a bas-de-page scene of Stephen preaching before three others. Image taken from f. 233v of Psalter ('The Queen Mary Psalter'). Written in Latin, with French image captions.

The concept of the Trinity is a central doctrine of Christianity that refers to the belief in one God who exists as three distinct persons: the Father, the Son (Jesus Christ), and the Holy Spirit. The three persons of the Trinity are equal in power and glory, and yet distinct in their roles and relationships with one another. The Father is the source of all that exists, the Son is the redeemer of humanity, and the Holy Spirit is the comforter and guide of the Church. The doctrine of the Trinity is rooted in the teachings of Jesus and the apostles, as well as in the early Christian Church's reflection on the nature of God and on the experience of God's presence in the world. The Trinity is a mystery that transcends human understanding and cannot be fully grasped by the human mind.

The BL Royal Manuscript Collection, also known as the Royal Collection, consists of over 2,000 manuscripts that were once owned by the British monarchs, including English and later British kings and queens from the late 12th to the 19th centuries. These manuscripts are notable for their historical and artistic value.

The collection was initially stored in various royal libraries and palaces, such as the Tower of London and Westminster Palace. During the English Civil War in the 17th century and the subsequent Interregnum, many royal treasures, including manuscripts, were dispersed and sold. Some manuscripts were lost, destroyed, or ended up in private hands.

In 1757, King George II donated the Old Royal Library to the British Museum (which later became the British Library), where the manuscripts were integrated into the museum's collections. This marked the formal establishment of the Royal Manuscript Collection within the British Museum.