The 24-year-old has spent the first half of the campaign with the Sky Bet League Two side and his spell was due to expire on 1 January 2018. All parties have now agreed to extend the loan until the end of the season. Jack has played 23 games in all competitions for The Cumbrians, who sit 14th in the table, seven points from the Play-Off places and eight clear of the relegation zone.

Dean Smith, Brentford FC Head Coach, said: “We agreed Jack could go to Carlisle because we felt he could play the games he needed. He has great potential but needs competitive football in order to improve. He has impressed while he has been there and Carlisle wanted to keep him. We have been pleased with the loan so far and were happy to agree. I wish Jack all the best for the rest of the season.”

Jack has had limited playing time at Brentford since he arrived four years ago. He joined The Bees in the summer of 2013 after being released by Watford and extended his contract in early 2015. That deal was extended in the summer until 2019. Jack made three appearances for The Bees in his first year at the Club. He has played four more games, seven in total, and made his first Sky Bet Championship appearance for The Bees in the Easter Monday draw with Barnsley earlier this year.

Jack made his professional debut on the last day of the 2012/13 Championship season for Watford as a substitute. He had started the day as third in line but injuries to the two main goalkeepers thrust him in to the role. Jack left Watford a few days later and joined The Bees having been on trial earlier that year. The goalkeeper has also represented the Republic of Ireland at Under-17 level.