Orthodox Saints of the Pre-Schism See of Rome
27th June
CLEMENT of CÓRDOBA, a martyr circa 298 in Córdoba (southern Spain) during the Diocletianic Persecution (303–313). St. Clement was most likely a member of the group led by St. Zoilus of Córdoba (vide infra).
DEODATUS of NOLA, a deacon to St. Paulinus of Nola (22nd June), then Archpriest of Nola (a suburb of Naples, Italy), and lastly successor of St. Paulinus to the See of Nola. St. Deodatus reposed in 473. His feast day is variously listed as either the 26th or 27th of June.
DESIDERATUS of GOURDON, a priest and anchorite in Gourdon 35 km/22 mi south-west of Châlon-sur-Saône, in the present-day region of Bourgogne-Franche-Comté in eastern France. St. Desideratus reposed circa 569.
JOHN of CHINON (TOURS), possibly a native of the British Isles, St. John was a sixth century anchorite in Chinon in the Diocese of Tours (west-central France). He was the spiritual father of Queen St. Radegunde of France (13th August), and known for his wonderworking.
ZOILUS and COMPANIONS of CÓRDOBA, St. Zoilus, a youth, and 19 others, martyred circa 301 in Córdoba (southern Spain), during the Diocletianic Persecution (303–313). His relics were translated to León (north-western Spain) in the late 11th century, and enshrined in a monastery there which was renamed San Zoilo de Carrión (St. Zoilo of Carrión).
Prior to the Schism the Patriarchate of Rome was Orthodox, and fully in communion with the Orthodox Church. As Saint John of Shanghai and San Francisco +1966 said “The West was Orthodox for a thousand years, and her venerable Liturgy is far older than any of her heresies”.
Details of British Saints excerpted from Orthodox Saints of the British Isles.
Details of continental saints from these sources.
In many cases there are several spelling versions of the names of saints from the British Isles. I use the Oxford Dictionary of National Biography version as the primary version with the more prevalent version in parenthesis e.g. Ceadda (Chad) of Lichfield.