"We are still hoping to make a signing on Friday but we won't be signing the Greek defender that came over for a few days," reveals Glenn.
"He enjoyed his time with us, and we enjoyed having him to see his ability and what he could do in an excellent practice ground game against Reading in difficult, windy conditions.
"But for one or two reasons we decided not to bring him to Upton Park for the rest of the season, so he has returned to Panathanaikos.
"There were a couple of factors that I don't want to go into detail about - that I don't need to go into detail about - that made us feel we wouldn't make the deal happen, but we are very aware of what he has to offer as he returns to his country.
"We are hoping, though, to conclude one more signing before the window closes on Friday."
Glenn strenuously denies, however, reports that claimed a swap with Sunderland involving Michael Gray and Don Hutchison was ever on the cards.
"That is not a deal that ever got up and running," emphasises Glenn, "we are happy to have Don fully fit again - he is now part of a very strong midfield, and is ready to step back into first team action as and when he is selected.
"As well as that strong midfield unit, and with Dons's versatility, he can also play very well as a striker which is what Bertie Vogts says he wants to use him as in a friendly against Eire in a couple of weeks' time."
As for the rest of it, ahead of the closure of the Premiership's first - and unwanted, by Glenn and others - transfer window, he adds:
"I think it will be very difficult to find a central defender that we want by the close of play on Friday; it is a position that no one has been able to fill - and I know that several clubs have tried in the Premiership.
"But I am still hopeful of one more signing by Friday so the player can be registered in time for the game against Liverpool."
Arsenal midfielder David Noble has been with the club this week, playing in the same game as Vokolos, and Glenn adds:
"Young David has been training with us for a few days and we are pleased with what he has shown us.
"We feel he has a lot of ability, and we hope to put a deal together that is suitable for him and us.
"He is highly rated, but it is very difficult for any young player to break through into Arsenal's first team.
"But we know he is a talented player and it is just whether we can make a deal happen or not."