Sigebert Buckley (b. c. 1520 AD; d. probably 1610) was a Benedictine monk in England, who is regarded by the Benedictines and by Ampleforth College in particular as representing the continuity of the community through the English Reformation.
Although the English Benedictines had been dissolved by Henry VIII in the 1530s, one solitary monastery was re-established in Westminster Abbey by the Roman Catholic Queen, Mary I of England 20 years later. After only a few years, her half-sister Queen Elizabeth I dissolved this monastery again. By 1607 only one of the Westminster monks was left alive: Father Sigebert Buckley.
Buckley survived until the reign of James I, by which time a number of Englishmen had become Benedictines in the monasteries of Italy and Spain, and had obtained a faculty from Pope Clement VIII (in 1602) to take part with the secular clergy and the Jesuits in the English mission. It was through the efforts of the English monks of the Cassinese or Italian Congregation that Buckley became instrumental in preserving monastic continuity in England. It is through Buckley that the English Benedictine Congregation lays claim to an unbroken continuity with the pre-Reformation monasticism of England.
Buckley's statement 
I, D. Sebert, otherwise Sigebert, priest and monk of the monastery of St. Peter, Westminster, of the Congregation of England of the Order of St. Benedict: lest the rights, privileges, insignia, should perish which were formerly granted by Princes and Pontiffs and which for some years, God so permitting, have been preserved in me the sole survivor of all the English monks: did at London in the year 1607, the 21st day of November, with the consent of their superiors receive and admit as brethren and monks of the said monastery D. Robert Sadler of Peterborough and D. Edward Maihew of Salisbury, English priests and monks professed of the Cassinese Congregation of St. Justina of Padua: and to them did grant, impart and assign all rights, privileges, ranks, honours, liberties and graces which in times past the monks professed and dwelling in the said monastery did enjoy. And the same by these presents I do again approve, ratify and confirm. And I do receive and admit as monks, brethren, lay-brethren, oblates of the said monastery and to them do grant, impart and assign all rights, privileges, as above, all those whom D. Thomas Preston of Shropshire, D. Augustine [Smith] and D. Anselm [Beech] Lancastrians, and D. Maurus [Taylor] of Ely have admitted or received as monks, lay-brethren, oblates, and to whom they have granted the rights, &c, as above: since to them I did grant authority and power so to admit, &c, as appeareth more at large in my letters of the 21st November 1607: the which [letters] as to all and each of their parts I do by virtue of these presents hold ratified and confirmed, and will so hold them in perpetuum. Given at Punisholt, otherwise Ponshelt, Anno Domini 1609, the 8th day of November, in the presence of the underwritten Notary and witnesses".
Notes and references 
- or possibly 1608
- baptised Robert Seabert, he was a native of Staffordshire, and had been professed and ordained in 1558 
- Anselm Cramer, Ampleforth: the story of St Laurence's Abbey and College, St Laurence Papers V. Hardback, 223 pp, 80 b/w
- H.Connolly, 'The Buckley Affair', in Downside Review 30 (1931) 49-74