Robertson, 20, cost Steve Bruce's side �2.85 million ($4.82 million, 3.6 million euros), according to the club website, while the fee for 21-year-old Maguire was �2.5 million. Both players have signed three-year deals.

Robertson joined Dundee United from Scottish third-tier side Queens Park just over a year ago and was named Scotland's Young Player of the Year after an excellent maiden campaign.

England Under-21 international Maguire, meanwhile, made 166 appearances for Sheffield United and was named the club's Player of the Year in each of the last three seasons.

"A lot of things attracted me to Hull City. But a big factor was the manager," Maguire told the club website.

"Steve Bruce is a great manager. He was a centre-back himself during his playing days -- and a very good one at that -- so I'm sure he'll be willing to pass on a bit of advice."

Robertson and Maguire join Jake Livermore, Robert Snodgrass, Tom Ince and Karim Rossi in arriving at the KC Stadium during the close season.

Hull, beaten 3-2 by Arsenal in last season's FA Cup final, open their Premier League campaign away to promoted Queens Park Rangers on August 16.