I just read somewhere that 'Perdita' means "the lost one". David Austin named this rose after a Shakespeare character. It's an older Austin (1983) that Austin is still selling, which tells you something about the quality: it's good. Rust and mildew resistance are excellent, rebloom is steady, growth habit is upright for an older Austin and it's a decent size--neither too big nor too small, about 4'x4' in my garden.
Where it fails completely is in the fragrance department--it has some, but not much. Otherwise an excellent cultivar that hasn't gotten quite the attention it deserves--you often read the praises of older more popular Austins like 'Mary Rose' and 'Tamora', but this one is equally good. Perhaps it is a little bit of a "lost one".