"He is coming to join us on a short term contract until the end of the season," declares Glenn, "and he believes he can show us enough in three and a half months for us to want to secure him on a longer contract - which is what we want him to do.
"We are going to know an awful lot more about him, and he is going to know more about us, come the end of the season.
"We are very positive about a young player that spent two years at Lilleshall with Joe Cole; they were partners in the midfield and David chose the Arsenal route while Joe chose West Ham, as everyone knows.
"He is a very good footballer, as we have seen in the two days training he has had with us and the friendly against Reading, he is comfortable on the ball, he knows his next pass before he receives the ball, and we just hope that we can get him up to the athletic side of the game - which is a must in the Premiership.
"He will have plenty of days training with the first team squad which I would assume with the size of the Arsenal squad would have been nearly impossible for him.
"If he has anything about him - and we hope he has - he will improve quickly and greatly training with our first team players."
Glenn has been one of the busier managers in the January transfer window, bringing in a quartet of players - with David not costing a fee - and he says:
"I am very grateful and happy to have been able to secure Lee Bowyer, Les Ferdinand, Rufus Brevett, and young David who we will be working hard to get in the first team squad for sure, but really is one for the future.
"Ferdinand, Bowyer, and Brevett are very much for today.
"I said I hoped to secure one signing, maybe two, and in the event the club has helped me to get three players who I am sure can help us survive."
A centre half was a target originally, but Glenn resisted the temptation to get one in just for the sake of appeasement.
"You just have to feel it is right for the club," he explains, "and it has been very hard to find exactly what we are looking for.
"And there are no clubs that have signed central defenders that have made us think 'how did we miss out on that one?'
"If that had happened I would have been worried about my contacts in the game; but central defenders are few and far between."
David, who was at Watford on loan last season, is 21 on Sunday.