Locke was originally supposed to miss this Sunday’s big game, but his wife Kate gave birth to their son George William Locke last weekend.
Former Pontypridd second row Locke will captain Merthyr from his usual position and is partnered in the boiler house by Nick White, while Edward Siggery, Osian Davies and Phil Rees form a formidable back-row.
Behind the scrum, Justin James and Richard Powell form an experienced half-back combination with Arron Pinches and Gavin Dacey in midfield.
Matthew Jarvis starts at full-back with Richard Carter and Kyle Evans on the wing.
“I missed the Carmarthen game last weekend due to Kate going into labour early,” said Locke.
“But he’s here now and fit and healthy. It’s my first baby so I’m over the moon.
“As long as I have some sleep the night before the final, everything will go fine. I look at George and think if I win the Cup it will be for him as well.
“We’ve done well over the last few years as we’ve kept building. But this cup final is a blank canvas for Merthyr as we’ve never been in a here before.
“It will be good to write a bit of history for Merthyr and get a nice win. It takes me back to when I was with Pontypridd.
“We are ready for them to attack from anywhere because as soon as you switch off for a second a quality team like Newport will punish you.
“When we lost to Newport at home in the league there was always next week, but you only get one shot in a final.”
This will be the Black and Ambers’ third final having lifted the cup twice before in 1977 and 2001.
Newport head coach Craig Warlow has selected a strong side as he looks to topple the Principality Premiership’s leading team.
Up front John Lavender, William Evans and Thomas Piper pack down in the front-row while Joseph Bartlett and Daniel Partridge start as the lock pairing.
Morgan Burgess, Kyle Tayler and Alex Everett form the back-row.
There is plenty of pace and invention in the back-line as Geraint O’Driscoll, Jonathan Morris and Elliott Frewen start in the back-three.
Chay Smith and Jonathan Morris start in midfield while Matt O’Brien and Ryan James are at half back.
“It’s been a long time coming and it’s about time we did something in the cup,” said Newport loose-forward Rhys Jenkins.
“The excitement is building in the city and everyone is getting behind us. Local businesses are tweeting about us and promoting us so it is very good for the city.
“There’s no doubt that Merthyr are a very strong team. We know what they will bring.
“They are a big and physical team with talent right across the field. It’s going to be a massive challenge but one we know we can take on.
“We’ve beaten them up there already this season. We might be the underdogs to everyone outside the squad.
“But within the squad we know what we are capable of. We’ve been up there and beaten them on their own patch and we’ve got nothing to fear.
“We know what we are good at and we will play our own game. We pride ourselves on our ability to play rugby so hopefully we can throw the ball around and entertain the crowd.
“We will hopefully bring a rounded game and take them on.”
Newport: Geraint O’Driscoll; Jonathan Morris, Chay Smith, Thomas Pascoe, Elliott Frewen; Matt O’Brien (capt), Ryan James; John Lavender, William Evans, Thomas Piper, Joseph Bartlett, Daniel Partridge, Morgan Burgess, Kyle Tayler, Alex Everett
Replacements: Henry Palmer, Nicky Boyce, Garin Harris, Andrew Mann, Lennon Greggains, Rhys Jenkins, Owen Davies, Haydn Palmer
Merthyr: Matthew Jarvis; Richard Carter, Gavin Dacey, Arron Pinches, Kyle Evans; Richard Powell, Justin James; Nathan Trevett, Rhys Williams, Joe Rees, Nick White, Craig Locke (capt), Edward Siggery, Osian Davies, Phil Rees
Replacements: Matthew Dwyer, Louis Jones, Rhys James, Ben Sier, Lee Evans, Adam Hoskins, Gareth Davies, Tom Riley
