 It is likely that much of Morris 's preference for medieval textiles was formed – or crystallised – during his brief apprenticeship with G. E. Street . Street had co @-@ written a book on Ecclesiastical Embroidery in 1848 , and was a staunch advocate of abandoning faddish woolen work on canvas in favour of more expressive embroidery techniques based on Opus Anglicanum , a surface embroidery technique popular in medieval England . 
