harry potter?

I don't know specifically about HP4, but David Bradley, who is in Mayor of Casterbridge, has played Mr. Filch in the first 3 HP movies.

Ciaran Hinds (Henchard) will play the young Dumbledore in the final two Harry Potter movies.

Piece of trivia - the names "Dumbledore" and "Hagrid" both appear in the same sentence in the novel "The Mayor of Casterbridge". The following sentence appears about 1/3 of the way into the book, when Elizabeth Jane is attempting to train herself to drop her provincial way of speaking:

"The sharp reprimand was not lost upon her, and in time it came to pass that for “fay” she said “succeed;” that she no longer spoke of “dumbledores” but of “humble bees;”, no longer said of young men and women that they “walked together,” but that they were “engaged;” that she grew of talk of “greggles” as “wild hyacinths;” that when she had not slept she did not quaintly tell the servants next morning that she had been “hag-rid,”, but that she had “suffered from indigestion.” "