The 20-year-old had an impressive 2020/21 campaign on loan with AFC Wimbledon, with that form rewarded with a new two-year contract earlier on this week.
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Albion’s pathway development manager David Weir said, “Ryan deserves the opportunity to show what he’s capable of at Championship level after a really good year at Wimbledon.
“He came on leaps and bounds there and this presents him with the chance to show what he has learned against a step-up in quality of opponent each week.
“This is an exciting chance for Ryan. We’re looking forward to closely monitoring how he progresses and wish him well for the season ahead.”
Longman netted nine times in 51 appearances for the Dons last season, as he helped them retain their League One status.
The Tigers on the other hand return to the Championship after a year out of the second tier, with Grant McCann’s team scooping the League One title last season.