Cyle Larin’s penalty in first-half stoppage time put Saints on course for round five but Oliver Skipp’s acrobatic equaliser early in the second half made it 1-1 at the end of normal time.

Managerless Leicester had not won since beating Cheltenham in round three and it took until the 19th minute for either side to create a chance.

Joshua Quarshie failed to deal with a high ball, allowing Jordan Ayew to get a shot away and his effort was beaten out by debutant goalkeeper George Long.

Saints had a lucky escape seven minutes before half-time when Stephy Mavididi’s shot was saved by the legs of Long before unwittingly being diverted onto his own bar by Oriol Romeu and then cleared off the line by Ryan Manning.

The hosts were gifted the lead as Samuel Edozie won the ball on the edge of the area and drew a clumsy foul by Caleb Okoli, giving Larin the chance to fire home from the spot.

Skipp levelled seven minutes into the second half with a brilliant overhead kick from six yards after Saints had been caught sleeping at a corner.

Saints would have re-taken the lead but for a superb piece of defending from Olabade Aluko to stop Cameron Archer tapping in from point blank range after Jakub Stolarczyk could only parry a Kuryu Matsuki effort.

Divine Mukasa should have won it for Leicester in stoppage time but put a free header from Harry Winks’ corner over while another corner was cleared off the line by Quarshie.

Bree headed a 109th-minute winner after Manning’s free-kick had flicked off the head of Leicester substitute Patson Daka into his path at the far post.