Mark Wilson has completed his move from Dundee United to Celtic, signing a four-and-a-half year deal.
Mark Wilson displays his new colours on Monday
The 21-year-old, who can play at full-back or in midfield, moves for a fee thought to be about £500,000.
"It's definitely a proud day. It's a club the family have supported all their life," admitted Wilson.
"I don't expect to break in straight away, but I'll get my head down in training and try to impress the manager," he added.
"I don't think it's really sunk in yet that I've signed for a club of this size. It's a privilege to get the honour and opportunity to come here and play for them.
"Over the next few days it will sink in a bit more when I get to meet the players and get into training. I'm looking forward to it."
Manager Gordon Strachan insisted the signing was not a reaction to recent performances in which the defence has leaked goals.
"The decision to sign Mark was taken a long time ago. It's not a knee-jerk reaction, it's about the future of the club," he said.
"When I first came to the club, (scout) Tom O`Neill said to me 'That's your man'.
"I said 'Great, but let me see for myself'. I'd seen him on television but I had to see him for myself.
"This has been in progress for six months without actually speaking to Dundee United or Mark. The progress was me turning up and watching Dundee United quite a lot, seeing Mark playing against us and then the decision was taken.
"We thought that we could afford it, we could do it and we should get on with it."
Asked if he would go straight into the Celtic team, Strachan added: "He must have a chance, but I can't guarantee anyone a first-team place when they come to the club.
"He can play football, he can get forward and he can tackle. He has the intelligence to take in information, he has hunger and an honesty about him.
"If you take into account all the factors, he is in with a half-decent chance."
BBC Scotland understands that Wilson himself will pick up about 25% of the transfer fee, with the remainder going to Dundee United.
"We didn't want to lose him but he had a clause in his contract stating that, if a club met the agreed asking price, he could go," said United chairman Eddie Thompson.