James Hook's 50 metre penalty three minutes from time allowed the Lions to maintain their 100 per cent record, but
"In the first-half we played well, but we let them back into the game with some basic mistakes," said Williams.
"They defended very well and stopped us from getting any real momentum going forward. Our set piece went well, but we didn't keep the ball as well in the second half.
"We'll take the win, though, and we are still unbeaten. Now we have to keep the momentum going on Tuesday against the Southern Kings and into the first Test.
"Every Saturday game on this tour we have failed to turn the screw when we've been in the lead. We gave too many silly penalties away."