League Two leaders Leyton Orient went down to a surprising FA Cup exit at Crewe with Bass Sambou hitting a stoppage-time winner for the hosts in Lee Bell’s first game in charge.

Orient were down to 10 men after Craig Clay’s 87th-minute dismissal at Gresty Road and were caught out when Kelvin Mellor charged down the right flank and crossed for Sambou who finished high into the net.

Richie Wellens fielded a much-changed side and despite their first-half domination, Orient could find no way past excellent Crewe keeper Arthur Okonkwo.

Charlie Kelman had a goal chalked off when he was ruled to have fouled Okonkwo before finding the far corner.

Okonkwo made saves from George Moncur and Kelman as well as pushing clear a powerful volley from Stephen Duke-McKenna. Moncur also crashed an angled effort onto the underside of the bar.

But at the other end, Lawrence Vigoroux needed to make an agile save to keep out a Dan Agyei header from Tariq Uwakwe’s corner.

After the restart Billy Sass-Davies went close with a set-piece header he planted just past the far post. Wellens drafted on Paul Smyth among a raft of changes in a bid to win the tie and the leading scorer was thwarted by a vital block from Mellor.

And after Clay was handed a red card for a late challenge on Lachlan Brook, it was Mellor providing the assist for Crewe’s winner.