Crawley booked their place in the second round of the FA Cup - but only just.
Reds were made to work hard by Ryman premier division Met Police before squeezing through 2-1 at Imber Court.
Josh Simpson had given Crawley the lead in the first half and the contest looked over when Billy Clarke doubled the advantage with 20 minutes to go.
But Met Police grabbed a goal back with eight minutes remaining and were only denied a replay by a combination of desperate defending and the woodwork.
Reds wanted an early goal to stamp their authority on the game and it so nearly came after six minutes when Dannie Bulman's 30 yard shot bounced down onto the line off the underside of the bar.
Josh Simpson had a penalty appeal waved away a couple of minutes later when he appeared to be tugged back just inside the area by Joe Dolan.
After weathering that initial threat Met Police settled into the game and were able to keep their visitors at bay as they defended in numbers.
Goalkeeper Jamie Butler was called into action for the first time in the 25th minute when he dived to push away Sergio Torres's shot from the edge of the area.
Butler was at fault though as Reds took the lead in the 36th minute. Butler raced out of his area as Simpson tried to get on the end of a through ball from Mike Jones but only suceeded in making it easy for Simpson to slot into an empty net.
Paul Jones had been a bystander at the other end but Met Police showed more ambition after falling behind with the Reds goalkeeper making comfortable saves from Allan Tait and Matt Smart.
The hosts will have been fairly satisfied to go in just a goal down at the break and began the second half well.
They nearly got an equaliser, too, when Howard Newton cut in dangerously from the left but his shot was tipped over by Jones.
Craig Brown had an even better chance in the 67th minute when he robbed Joe Walsh of the ball 25 yards out but he dragged his shot wide when Tait was well placed at the far post.
Crawley doubled their lead three minutes later when Gary Alexander did well to turn at the near post and cross for Clarke to tap home from close range.
Met Police refused to give up, however, with Jones pushing a header from Steve Sutherland around a post and Jay Lovett heading over at the far post.
The home side got the goal they deserved with eight minutes to go. Brown's 20 yard shot came back off the bar and Tait was on hand to knock in the rebound.
Suddenly Reds were under pressure and Met Police almost grabbed an equaliser with three minutes to go when Jones was at full stretch to turn over a header from Newton.
The home side came even closer to forcing a replay deep into injury time when Kyle McFadzean cleared a shot off the line from Jay Lovett and then Sutherland hit the post.