The 40-year-old defender, who has played more than 100 league games for four different clubs, has been a mainstay at the heart of the Tranmere Rovers defence in the last two seasons - and will join the Saddlers when his contract expires on July 1.
The defender, who began his career at Everton, playing 14 times for the Premier League club, said he was sold on the project as soon as he spoke with Michael Flynn.
He said: "I initially spoke to the Head Coach, we had a brief spell playing together many, many moons ago and we have always kept in touch and we have respected each others careers from afar," Clarke began.
"I had a call from him asking about my availability and having spoken to him and hearing how passionate and enthusiastic he was about one, bringing me into the club and secondly about what he wants to do and how he wants to move the club and the team forward, it was something that really, really appealed to myself.
"With us knowing each other from way back when, there is an initial respect, there is an initial knowledge of each other’s capabilities and what we are about as a player, as a manager and also as a person, probably more importantly.
"The initial conversation was not a long one but I think we both realised that we were thinking very much alike and were wanting to make the move happen as quickly and as smoothly as we possibly could."
Clarke is one of just a few players in their 40s still playing in the EFL - with Newport County's Kevin Ellison still plying his trade. Clarke believes that even though others look at his age - it is just a number for him and he gets on with the job in hand.
He added: "To me, my age isn’t an issue. To lots of other people, maybe it is but I love being out there, I feel good.
"When younger players or other players ask about how you do it, to my way of thinking, it was all I ever wanted to do as a kid to be a footballer.
"Certainly the older you get and the more experienced you get, you have to take care of your body and everything has just become a habit and a way of life.
"I do everything I possibly can to make sure I am in the best shape I possibly can be to be available for selection as often as is possible."
Clarke's career has seen him turn out for Blackpool on two occasions, Coventry City, Port Vale, Southend United, Huddersfield Town, Bury, Oldham, Fleetwood and then Tranmere - where played in every single league game over a two year period.
Flynn added that Clarke's professional nature was a big factor in bringing him to the club.
"Peter is a fantastic professional, he is a leader," said Flynn.
"He was the only outfield player to play every minute of every game last season and he was in the League Two team of the year.
"I have known him a very, very long time and I have never come across a bad word said about him.
"He epitomises everything of a true professional. He looks after himself, that is why he is still playing at the age of 40 and he will give us an unbelievable amount of leadership for the rest of the group."