A penalty a minute from time from substitute Matej Vydra earned Watford all three points at Vicarage Road against Peterborough United.
The first half was a very quiet affair with very few chances in front of goal. Posh made a bright start, forcing a corner inside the first 14 seconds, which Tommy Rowe headed over the bar.
Tyrone Barnett headed over with two separate chances before Watford came close to the breakthrough as Daniel Pudil curled a free-kick onto the top of the crossbar from around 25 yards.
Posh made a change at the break with Kgosi Ntlhe replacing Rowe at left wing back. Posh won a corner inside the first minute of the second half, but despite a good delivery, it came to nothing.
Bostwick then blocked a fierce Forestieri shot before Bobby Olejnik made a stunning stop to push a Chalobah effort around the post. Forestieri was causing a lot of problems, his 25-yard shot went wide before Cassetti went close as the Hornets continued to threaten.
Chalobah then struck the inside of the post with a low drive with Olejnik clutching the rebound. Grant McCann replaced Alcock on the hour mark with Bostwick dropping back into the centre back area of the pitch.
Grant McCann fired over on 66 minutes before Darren Ferguson introduced Saido Berahino for Sinclair in the final change of the afternoon.
Forestieri saw an effort cleared off the line by Brisley after flicking the ball past Olejnik on 68 minutes as Watford continued to dominate. The lively Forestieri fired into the side neetting before Gianfranco Zola introduced another front man in the form of Matej Vydra.
At the other end, on 79 minutes, George Boyd headed straight at goalkeeper Almunia after a glorious cross from substitute Berahino while Barnett also saw a shot blocked as Posh pushed forward.
Right at the death when Posh looked like they would hang on for a point, Ferdinand inexplicably felled his man in the box and the referee awarded a penalty which VYDRA smashed down the middle to give the home side the lead.
Final Score: Watford 1-0 Posh
Watford: Almunia, Hall, Hogg, Deeney (sub Geijo 85min), Doyley, Pudil, Abdi (sub Vydra 72min), Cassetti, Hoban, Chalobah, Forestieri (sub Yeates 88min). Unused subs: Bond, Murray, Anya, Thompson, Geijo.
Posh: Olejnik, Alcock (sub McCann 60min), Brisley, Little, Knight-Percival, Rowe (sub Ntlhe 46min), Boyd, Bostwick, Ferdinand, Sinclair (sub Berahino 66min), Barnett. Unused subs: Richardson, Zakuani, Swanson, Tomlin.
Attendance: 15,950 (1,415 Posh fans)