Hi there
Sorry, I can't see any record of this marriage in Halesworth.
I also gather from your other posts that there is a bit of a question mark over Robert's details anyway. The nearest Halesworth record I can find refers to Arthur Robert Mills (s/o William & Emma Mills) born 27 Aug 1863, baptised 18 Oct 1863. This William was an attorney's clerk. Worth investigating?
Dave