However, despite the lateness of the additions, Bilic revealed that the arrivals had been in the pipeline for some time.
"I think we've done a good job. That's what we wanted and it looks like the last day was a hectic day, but really the deals were done a few days ago and we just needed the papers [finalised]," the Croat told the club's official website.
"We knew from the start what we wanted and for a few players we waited until the end because it was impossible to get them done earlier because of their clubs."
"We were patient and we said we'd wait until the last day and have a back-up if necessary. That's why maybe it looks like it was all done on the last day, but it wasn't."
In total, 12 players signed on at Upton Park this summer.