Cook called up as cover as Vaughan opts to stay with squad

However, the diagnosis made by his orthopaedic specialist in England, who viewed the scans sent from Lahore, has allowed the England captain to remain with the squad where he will continue to have treatment. Quite what Vaughan has done to the knee is yet to be revealed, but we must assume that he has not torn his cartilage and he is in no danger of causing further damage to the joint.

There appears almost no chance of Vaughan playing here on Saturday and there must be serious doubts that he will be fit for the second Test in Faisalabad which starts in 10 days' time. There is no reason why England should rush their decision on Vaughan, and the team will only benefit from his continued presence.

The uncertainty over Vaughan's fitness has caused England to fly Alastair Cook out as cover. The 20-year-old Essex opener will travel to Pakistan before the first Test begins, but has little chance of playing in the game.

"Obviously, I am thrilled and I am just looking forward to joining up with the squad," Cook said. "I heard on Tuesday there was a possibility and then found out just before the announcement. It is a great opportunity to go out there and learn about what Test cricket is like.

"I think Owais Shah or Robert Key would have gone if they were fit," Cook added, "but it is nice to get the call."

David Graveney, England's chairman of selectors, explained why Cook had been selected ahead of Ed Joyce and Vikram Solanki, players with greater first-class experience. Graveney said: "Alastair Cook has been called into the squad as we felt we needed an opening batsman to provide cover not only for Michael Vaughan, but also for Andrew Strauss, who is expected to fly home before the third Test to attend the birth of his child.

"Alastair had an outstanding season for Essex last summer, is a member of our National Academy squad this winter and we believe he has the potential to succeed at international level."

The England selectors also announced that Shaun Udal and Kabir Ali will be added to the one-day squad, which is scheduled to play five limited-overs games next month.

The pair replace the fast bowlers Simon Jones and Chris Tremlett, who were both forced to withdraw with injury.

"Our original selection included only one specialist slow bowler," Graveney said. "But the captain and coach have now had an opportunity to assess the conditions in Pakistan and we have decided that it would be prudent to add Shaun Udal to the one-day squad.

"Kabir Ali's bowling should be well suited to the conditions and this tour will give him another opportunity to stake his claim for a regular place in the side."

Udal said: "To have played in the two tour matches here for England and now be included in the one-day squad is a dream come true."