Seems a humble guy. Speaks well but it's now time to do the talking on the pitch. Speaks several languages fluently, which may also improve communication on the pitch.
Here are a few of his tweets from this evening:
@SMignolet: Delighted, very proud and priviliged to be the first Belgian signing for such a big club @LFC #YNWA Many thanks for all the reactions!
@SMignolet: Also want to thank @SAFCofficial for the three amazing years I had in Sunderland.I will never forget the support I received from all of you!
@SMignolet: Especially the safc supporters!!!
Welcome to the club Simon. Give it your best!