West Ham have confirmed Tomas Soucek has joined the club on a permanent deal and signed a four-year contract.
The Czech Republic international midfielder has impressed since arriving at the London Stadium in January on loan from Slavia Prague.
The Hammers moved quickly to sign Soucek after securing their Premier League status with a 1-1 draw against Manchester United on Wednesday.
Moyes told Sky Sports News: “I have always believed it would be a permanent deal because I knew it was subject to us being in the Premier League and I always felt that we would be a Premier League club so I never really had any great worries about Thomas.
“The biggest concern was how well and how quickly he could fit into the Premier League. I think all the other things connected to him were good – he could score, he could run, he was a good footballer. So it was more to see how he would fit in.
“I was always confident he would be here with us. But I am glad to get it out of the way because I’ve been asked the question a few times.
“Obviously, we are glad he is going to be a West Ham player for a good period to come.”
Soucek has scored three goals in 12 Premier League appearances for West Ham so far this season.