"I have been more and more impressed with Peter since I have met him; he has a terrific mentality and I am sure he will become a vital member of our side."
On his move to Huddersfield, Clarke said: "It has been quite an easy decision to make, given the ambition and enthusiasm of the manager, the chairman and the staff around the club.
"I want to play at the highest level I possibly can, which is how it should be, and given that the ambition of the club matches my own ambition the decision was an easy one.
"The manager has seen me play and he knows what he will get. I will do a job for the greater good of the team."
Clarke began his career as a trainee with Everton and made nine appearances for the Toffees before moving to Blackpool in 2004.
After 84 appearances at Bloomfield Road, he moved to Southend in 2006 following their promotion to the Championship.
He was named the club's player of the year last season, during which he scored the equaliser in Southend's 1-1 draw at Chelsea in the third round of the FA Cup.
He leaves Southend after a total of ten goals in 124 appearances.
He is a leader, which is what I want throughout the spine of my side
Huddersfield manager Lee Clark
Terriers manager Clark added: "He is a leader, which is what I want throughout the spine of my side.
"We need strong, aggressive players who will not be pushed aside when it comes to the physical element of the game because then the good footballers we have will be able to get on the ball more.
"We need the right set of players to be here come August, so everyone - myself included - will have to be patient.
"There is no point in rushing out and bringing in poor substitutes - I will get the right people into the club."
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