Stuart Lancaster was content with England's performance in their 38-18 win over Scotland, but admitted there was work to be done.
England ran in four tries and dominated the contact area against the Scots, yet were unable to take a number of opportunities in each half.
Travelling next weekend to face Ireland in Dublin, Lancaster admits that the fixture will be a significant step up and one that England will be ready for.
"I'm pleased for the players, but there's plenty of work to do," said Lancaster.
"I was happy with the start but then we conceded the early try - it was poor execution, a poor kick and a poor chase which has hurt us in the past so we need to work on that.
"We are delighted with the way he (Twelvetrees) took it to get the try but his confidence and composure has been good all week. It shows he is ready to make the step.
"This time last year we had seven players making their debuts and with Billy making his we have a young side. We are bringing on 20-odd-year-olds and it is great for us as a squad.
"With Manu coming back into the equation - which we're pretty sure he will - we have got some selection dilemmas.
"People underestimate how long it takes to pull a cohesive team together. We needed to create a new sense of direction off the field which we have done. There have been ups and downs but we have always learnt as we've gone along.
"The last two weeks have been invaluable in going over the lessons we learned in the autumn. Our cohesion was excellent and it has given us a good foundation to go into Dublin.
"Clearly we will have to step up. Ireland are an outstanding side and their first-half performance today shows it's a big step up. We went there two years ago on the back of four from four and came home with our tails between our legs.
Lancaster added that the extent of Ben Morgan's injury would be revealed in the next 24 hours, after the number eight was forced off with an ankle sprain.
"It's not too serious but it's also too early to tell how long he will be out for," stated Lancaster.
Attack coach Mike Catt was delighted with the performances of Owen Farrell, who picked up the Man of the Match award after another strong performance at Twickenham, and also debutant Billy Twelvetrees who finished with a try on debut.
"That mental toughness that [Owen] possess was obvious again today," said Catt.
"He produced quick ball continually and we had Scotland on the rack two or three times which gave the guys like Billy and Brad the chance to work on the front foot.
"The nice thing [with Twelvetrees] was his urgency - he wanted to get his hands on the ball. He has done the basics extremely well."
by Ben Coles