With British and Irish Lions prop Alex Corbisiero's absence for long periods of the season, Waller stepped up to be counted in the Saints front row in 2013/14.
The Kettering-born 24-year-old's form was rewarded with an England Saxons selection in January, which this morning became a call-up for England's squad for the June tour of New Zealand.
The news came hot on the heels of the Aviva Premiership final, in which Waller's 100th-minute try - the tenth of his Saints career - saw the Academy graduate win the game against Saracens to make his club champions of England for the first time.
"Alex has had an unbelievable year," Hartley said. "I'm not going to say he's been an unsung hero, because he's had recognition, but he's finally come into his own as a player.
"Alex Corbisiero started today, but Alex Waller's played all season and it's perfect for us to have two class props. For Alex to come on, bash his eye, and then to score the try is testament to his character as a bloke.
"I can't think of anyone more deserving of a test shot and I feel like a proud dad! He's come through the Academy, is a close friend of mine, and I can't wait to tour with him. He deserves to get England honours."
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