As expected the Test squad contains all 12 of the players who guided England to a 2-1 win against Australia in the Ashes this summer.
Loudon and Tremlett will be making their first overseas trip with the senior squad while Udal, who has played 10 one-day internationals, makes his first trip since touring Australia in 1994-5.
He is rewarded for an outstanding county season.
Prior is included as the reserve wicketkeeper to provide competition for Geraint Jones, but the big surprise is the inclusion of Loudon as a third spinner ahead of Worcestershire’s Gareth Batty, who has performed that role for the last two winters.
"In choosing our Test squad, the area that involved the most discussion was the choice of spin bowlers," revealed Graveney.
Graveney dismissed concerns over the age of Udal, who has played 10 one-day internationals, but makes his first trip since touring Australia in 1994-5.
"Shaun Udal is an experienced spinner and based on his performances this summer we felt he merited inclusion ahead of other candidates such as Gareth Batty, Richard Dawson and Graeme Swann," said Graveney.
Both Tremlett and Lancashire’s James Anderson have been included as back-up seamers and their participation in the three-Test series may depend on the fitness of Glamorgan’s Simon Jones, who has been included subject to fitness.
Jones, who claimed 18 wickets in the historic Ashes series triumph, missed the final Test at the Oval with a right-ankle problem, has been included but may be ruled out if his injury requires surgery.
"Simon Jones has been included in both squads subject to fitness," confirmed Graveney.
"With regard to the wicket-keeping position, the selectors were aware of the credentials of Chris Read, Matt Prior and James Foster but Matt has been part of the one-day squad before and we feel he’s the best candidate to understudy Geraint Jones on this tour."