Very Interesting link, Bajansailor.
Andy as said they had very heavy duty steel cables welded to the side of the ship near the bow, I have circled these, and the cables were hung down the length of the ship ready for launch, circled again.
Also if you watch the video again, you will see them going taugh at the bow at 33secs into the clip.
Quite a sight.
It doesn't always work though, a few years ago they launched a ship there, and it kept going and hit the land on our side, resulting in a huge dent it the back, and a while in the dry docks getting repaired afterwards.
Cheers
Al.