Maundy Thursday commemorates the events of the night before Christ's crucifixion: the Last Supper, the institution of the Eucharist, the washing of the disciples' feet, and the agony in Gethsemane. The name 'Maundy' derives from the Latin mandatum novum — 'a new commandment' — from John 13:34, spoken after Jesus washed his disciples' feet. The earliest evidence of a distinct liturgical observance on this day comes from the late fourth century. The pilgrim Egeria, writing around 384, describes elaborate Jerusalem services including an afternoon Eucharist at the Martyrium basilica and an evening station at the Imbomon (the traditional site of Jesus's teaching on the Mount of Olives), concluding with a nighttime procession to Gethsemane. By the time of the Apostolic Constitutions (c. 380), the day was established as a fast day. Augustine of Hippo (Ep. 54, to Januarius) attests that by around 400 the day was celebrated with both a morning and evening Eucharist — the evening celebration deliberately recalling the hour of the Last Supper. The foot-washing ceremony (mandatum or pedilavium) became a standard Western liturgical practice by the early medieval period. The seventh-century Ordo Romanus documents the stripping of altars, and the Gelasian Sacramentary provides proper prayers for the day. The Eastern churches developed the day under the name 'Holy and Great Thursday,' with emphasis on both the Last Supper and the Passion beginning at Gethsemane.

The liturgical customs of Maundy Thursday are among the richest in the Christian year. The stripping of the altar after the evening Eucharist — removing cloths, candles, and ornaments to leave the sanctuary bare — dramatically enacts the desolation of Gethsemane and the abandonment of Christ by his disciples. This practice is attested from at least the seventh century (Ordo Romanus) and may be older. The washing of feet, whether performed by the presider on members of the congregation or as a mutual act, recovers the dominical command of John 13 and has been practiced in both East and West, though with varying emphasis — in England, the monarch's participation in the Royal Maundy is documented from the thirteenth century. The reservation of the Blessed Sacrament and the watch before the altar of repose recall Christ's words in Gethsemane: 'Could you not watch with me one hour?' (Matthew 26:40). The Tenebrae office — a service of progressive darkness in which candles are extinguished one by one — is historically associated with the Triduum evenings, and the BCP 2019 provides for it on this night. The evening marks the beginning of the Paschal Triduum — the three-day liturgy spanning Thursday evening through Easter Day that forms the single most important liturgical event of the Christian year. The collect focuses on the institution of the Eucharist specifically, grounding the day's devotion in sacramental theology: what was given on this night continues to be received at every celebration of the Lord's Supper.

Alphege (Ælfheah) was born around 954 and entered monastic life as a young man, eventually becoming an anchorite at Bath known for his extreme asceticism and spiritual discipline. He was appointed Bishop of Winchester in 984 and served with distinction, building a reputation as a disciplinarian and reformer of monastic practice before being elevated to Archbishop of Canterbury in 1006, succeeding Ælfric.

His tenure as archbishop coincided with the most devastating phase of the Viking raids on England. In September 1011, a Danish army commanded by Sweyn Forkbeard besieged and captured Canterbury, taking Alphege prisoner along with many of his clergy and citizens. The Danes demanded a ransom of three thousand pounds of silver—an enormous sum that Alphege refused to pay, insisting that the wealth of the Church belonged to the poor and could not be used to purchase one man's freedom, even his own. This decision reflected a theological conviction that the Church's resources were sacred and inviolable.

For seven months Alphege remained in captivity, reportedly maintaining his episcopal ministry and celebrating Mass in captivity. On April 19, 1012, at a feast in Greenwich, his captors—reportedly drunk on wine—grew impatient with his refusal to authorize ransom and attacked him. According to the Anglo-Saxon Chronicle (D manuscript), they pelted him with ox bones and remnants of their meal. A Danish Christian named Thrum, moved by compassion at the violence, struck Alphege with the back of an axe, presumably to end his suffering. He died of his wounds shortly after.

Alphege's body was initially left with the Danes but was soon recovered and taken to London, where it was given honorable burial. His cult grew rapidly, and by the early 12th century he was widely venerated as a martyr-bishop whose death exemplified pastoral sacrifice. He remained the most widely commemorated archbishop of Canterbury until Thomas Becket's canonization in 1173.

Traditionally, Alphege was venerated as a martyr-confessor whose steadfastness under captivity exemplified apostolic courage. According to Osbern of Canterbury, miracles of healing occurred at his tomb almost immediately after his martyrdom. When his body was translated from London to Canterbury in 1023 by Archbishop Æthelnoth, it was reportedly found to be incorrupt—a sign interpreted as confirmation of his sanctity, though the details of the translation account may be hagiographic embellishment.

A later tradition held that Alphege appeared in vision to Lanfranc, the post-Conquest Archbishop of Canterbury, urging the restoration of his shrine. The cult of Alphege was especially strong in Canterbury and Winchester, the two sees he had served. Uniquely among archbishops of Canterbury, Alphege was invoked as an intercessor by later martyred bishops, most notably by Thomas Becket, who reportedly prayed at Alphege's tomb before his own martyrdom in 1170 and saw his predecessor as a model of episcopal courage.