It does not need them because the program was made in England and they speak English, what you should ask is there any American english subtitles. We in britain watch many programs from the Usa without any subtitles whatsoever and over the years we have learned to understand American English, which gives us much more enjoyment in understanding American culture.
For people who are hard of hearing, subtitles and/or closed captioning can make the difference between understanding what's going on and missing key points. This is especially true with movies/tv where the plot is largely moved ahead in dialog.
Repeating the original question - is the DVD set subtitled in English or Closed Captioned?
I watched my first WIRE IN THE BLOOD DVD last night.
The British accent is clear for all almost the actors particularly Robson Green and Hermione Norris. No cockney nor Welsh. See Stephanie DuPre's review. She mentions the discs that have subtitles (to understand the British accents) and close captioning. And better extra features. The features on these discs are merely bios of the main characters and the author.
Ok, but if anyone is hard of hearing the accent of the actor (British, american, or Welsh) does not really matter, even the best-spoken english (or french, or portuguese) is difficult to understand for the persons that are hard of hearing. So, unless you have a perfect ear and, (God help you), still has this perfect hearing 10 years from now, closed-captions and/or subtitles should be an obligation, because, no pun intended, no one of us is getting any younger. And old age usually comes with loss of hearing. So a criticism about the difficult of the understanding english without subtitles is hurtful for the disabled persons and also for the elders!