The Sheffield-born centre-back was an injury doubt for the tournament with the ankle ligament damage which kept him out of Manchester United's Europa League final in May, but has now recovered sufficiently to take his place for the Three Lions's second group game, at Wembley.
Manager Gareth Southgate must now decide if the former Hul City and Sheffield United player should come into the starting line-up, either in place of Tyrone Mings or perhaps alongside him if England opt to match Scotland s back three.
"Harry will be involved," confirmed Southgate. "The decision we've got to make is whether he's ready to start but we're really pleased with his progress. His trained with the team for four or five days now and had no reaction.
"Each session he's involved in he gets more confident and I think he's on a really good path."
All 26 England players trained on Thursday, leaving Southgate with some difficult decisions after his team started with an impressive 1-0 victory over Croatia.
Southgate's opposite number Steve Clarke confirmed Kieran Tierney will play after missing Scotland's defeat to Czech Republic.
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