The No 8 linked up with the squad in Auckland tonight and will train with them for the first time in New Zealand tomorrow.
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Waldrom flew out as temporary cover for Nick Easter on Wednesday and although the Harlequins forward is recovering from a sore back it has been decided to add the Leicester Tigers back row and make the party back up to 30.
England Team Manager Martin Johnson said: “Nick is making good progress as is Matt Stevens but with Thomas now out here it makes sense to get him into the squad officially so he can join in with training. We also owe it to Leicester to make a decision so that they can plan accordingly without him.”