Gabriel Martinelli scored a superb hat-trick as Arsenal came from behind to beat Portsmouth 4-1 at Fratton Park and book their place in the FA Cup fourth round. 

Despite making 10 changes to their starting line-up, Mikel Arteta’s side recovered comfortably after an early scare against the Championship hosts.

Portsmouth stunned the visitors inside three minutes when Colby Bishop finished clinically to give the home crowd hope of another FA Cup upset. 

That optimism was short-lived, however, as Arsenal responded almost immediately, levelling just five minutes later when Christian Norgaard’s corner was forced into the net off Portsmouth midfielder Andre Dozzell.

The equaliser settled Arsenal, and they began to dominate possession and territory.

Their pressure told again after 25 minutes when Martinelli flicked in a Noni Madueke corner at the near post to put the Gunners ahead. 

Madueke had a chance to extend the lead before half-time from the penalty spot, but the winger dragged his effort wide.

Arsenal continued to control the game after the break, and Martinelli struck six minutes later in the second half. 

Quick thinking from Myles Lewis-Skelly led to Gabriel Jesus driving a low cross into the box, where Martinelli was on hand to tap in from close range for his second of the night.

The Brazilian completed his hat-trick in the 72nd minute, once more capitalising on a corner as he flicked the ball on at the near post and into the net. 

The goal underlined Arsenal’s strength from set-pieces and extinguished any remaining hopes of a Portsmouth comeback.

There was still time for a moment of history as 16-year-old defender Marli Salmon became the youngest player ever to feature for Arsenal in the FA Cup.

For Portsmouth, the early goal proved a rare highlight, while Arsenal marched on confidently, with Martinelli’s treble taking his tally to nine goals in all competitions this season.