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First-half goals from Paik Seung-Ho and Demarai Gray secured all three points for Chris Davies's side at St. Andrew's @ Knighthead Park.

The Blues carried the greater attacking threat during the opening 45 minutes.

Nathan Baxter made a smart save to deny Phil Neumann, but the Watford goalkeeper was powerless on the half-hour mark, when Paik stole possession in the visitors' half and drilled home.

The host side doubled the lead two minutes before half-time, with Gray turning home Jay Stansfield's deep cross at the far post.

Javi Gracia's side responded well after the break. Marc Bola tested James Beadle, before Othmane Maamma halved the deficit in the 61st minute.

It was the Moroccan's first goal for the Hornets, though it proved academic as Birmingham held on for victory.

Birmingham registered its first victory in eight league meetings between the sides, and only its second in 13 encounters.

The Blues have claimed 20 points at home this season, the joint-most in the Championship along with leader Coventry City.

Watford, which stays 15th in the table, missed the chance to move into the top half, suffered its first defeat in six league matches.