Middlesbrough cruised into the fourth round of the FA Cup as five unanswered second-half goals secured a 5-0 win over Peterborough.

Britt Assombalonga's double was supplemented by strikes from George Friend, Lewis Wing and Ashley Fletcher to provide Tony Pulis' Championship promotion hopefuls with a convincing win over lower-league opposition.

There was also a piece of history at the Riverside, with goalkeeper Dimi Konstantopoulos becoming Middlesbrough's oldest ever player at the age of 40 years and 38 days.

Twenty-six places separated the two sides at kick-off, but while the gulf was obvious by the full-time whistle, it was League One Peterborough that looked the more threatening initially.

Former Newcastle striker Ivan Toney caused some early problems, but when he found himself in an inviting position midway through the first half, he lacked the composure needed to make the most of it.

Toney turned neatly inside Friend in the area, only to balloon a harmless shot over the crossbar from eight yards.

That was Peterborough's best opportunity, although it was not their only one with Siriki Dembele whistling a low shot just past the post and Ryan Tafazolli heading Louis Reed's corner wide of the upright.

Middlesbrough's first-half display was disappointing, with Conor O'Malley only really forced to make one first-half save. Even that was a routine one, with the Peterborough goalkeeper claiming Rudy Gestede's flicked header from debutant Rajiv van La Parra's cross.

Pulis would have demanded much more from his side in the second period, and his half-time words had an immediate impact as Middlesbrough scored two goals within five minutes of the restart.

There was an element of fortune to the home side's opener, with Fletcher's shot from the edge of the area taking a huge deflection as it threatened to loop over O'Malley. The keeper did well to claw the ball onto the crossbar, but it rebounded invitingly for Assombalonga, who was able to head home.

Three minutes later, and the game was effectively settled as Middlesbrough quickly doubled their lead.

Friend found Fletcher down the left-hand side, and after his team-mate beat Joe Ward to deliver a low cross, the wing-back continued his run to sweep home a first-time finish from the edge of the six-yard box.

It was Friend's third goal of the season, and while Reed drilled a first-time volley wide narrowly after, Peterborough never looked like hauling themselves back into the game.

Their task was made all-but-impossible shortly after the hour mark, with Wing scoring the goal of the game. The half-time substitute picked up possession midway inside the Peterborough half, and with his opponents backing off, he lashed past O'Malley from 25 yards.

A fourth goal arrived with 20 minutes left, with Gestede's back-heel bamboozling the entire Peterborough defence, and Assombalonga slotting home his second of the afternoon as he raced unchallenged into the box.

The scoring was completed in the 87th minute, with Fletcher flicking home Paddy McNair's right-wing cross with a first-time volley.