This picture has been picked up on a number of not-so-credible Orthodox Jewish news sites (such as Gruntig or Matzav). A number of more credible Israeli Hebrew-language news websites have stories on it as well (see Kikar Shabbat and Mako for example).
From the Mako site (and through Google translate):
The 21-year-old star decided to put on the tefillin after meeting T. Caleb Friedman at his private school in the British capital. Radcliffe told Friedman that he does not remember whether to place his right or left hand on the mezuzah, and in response, Friedman pulled out the tefillin, as published on the Chabad Online website. Radcliffe was surprised by the offer, but responded positively. After wrapping himself in a tallit, one of the students who witnessed the event was very excited and documented the rare moment on the cell phone camera.
Is it an authentic picture of Daniel Radcliffe? Is it Daniel Radcliffe speaking Hebrew in the recording?