Transfer deadline day was a busy one on the red side of north London.
There were loan recalls, departures, an extension and a permanent farewell on an action-packed day in N5.
Here's what happened and when on deadline day:
11am: Matt Smith joins Charlton on loan
We kicked off the day by recalling Matt Smith from his Swindon Town loan, before revealing he had joined fellow League One side Charlton Athletic until the end of the season.
Our Hale End graduate had made 24 appearances for the Robins, scoring his first senior goals against Shrewsbury Town and Rochdale, while also claiming assists against Charlton, Bristol Rovers and Burton Albion.
The 20-year-old trained with his new team-mates for the first time on Sunday and is available for the Addicks' next game, at home to Portsmouth on Tuesday. He has been assigned shirt No 18.
"I'm really excited," Matt told Charlton's website. "I feel I can learn a lot off the manager and from the experienced players here. It’s a new challenge for me and ultimately I want to come here and help the team get promotion and have a strong second half to the season.”
7.30pm: Joseph Olowu joins Wealdstone on loan
Joseph Olowu was the next youngster to depart on loan, when he joined National League South side Wealdstone for the remainder of the 2020/21 season.
This will be our 21-year-old defender's second spell away from the club, after spending time with League of Ireland Premier Division side Cork City last season.
Joseph will be hoping to get his first taste of National League South football on Tuesday, when Wealdstone welcome Maidenhead United to Grosvenor Vale.
9pm: Zech Medley joins Kilmarnock on loan
Zech Medley then switched south-east England for south-west Scotland when he returned from his loan at Gillingham to link up with Kilmarnock.
The 20-year-old defender had made 12 League One appearances during his spell with the Kent-based side, but heads north of the border to bolster Killie's defensive options, following recent injuries to regulars Kirk Broadfoot and Stuart Findlay.
Zech was the second Premier League youngster to touch down in Rugby Park ahead of Tuesday's Scottish Premiership fixture against Celtic, with Crystal Palace's Brandon Pierrick also moving to East Ayrshire.
10pm: Shkodran Mustafi joins Schalke in permanent deal
Shkodran Mustafi ended his four-and-a-half-year stay in north London by joining Schalke in a permanent transfer.
The 28-year-old World Cup winner joined us from Valencia in August 2016 and has since been a prominent part of our backline, making 151 appearances during his time at the club.
Technical director Edu said: “We thank Musti for his contribution at Arsenal which has spanned four-and-a-half years, more than 150 appearances and a prominent role in two FA Cup wins. Everyone associated with the club wishes Musti and his family the very best wishes for the next chapter in his career.”
Mikel Arteta said: “Musti has been a key player for us for a long period of time. He played a very important part in my first season as manager and I’d like to thank him for his professionalism and for always being ready when called upon. Everybody at Arsenal wishes Musti well at Schalke.”
Shkodran links up with Sead Kolasinac in Gelsenkirchen. Our Bosnian defender captains his boyhood club, having re-joined them on loan in January.
10.55pm: Ainsley Maitland-Niles joins West Bromwich Albion on loan
Ainsley Maitland-Niles became West Bromwich Albion's fifth signing of the January transfer window, joining the Baggies on loan until the end of the season.
The 23-year-old has been with us since he was six and has progressed through the ranks to make 121 appearances for our senior side.
This is Ainsley's second loan spell away from north London, having spent time with then-Championship side Ipswich Town in 2015.
Technical director Edu said: “We wish Ainsley the best of luck for his time with West Bromwich Albion. He deserves the opportunity to play consistently, which is what he needs for his club and international career ambitions and we fully support him with that.”
Mikel Arteta said: “Ainsley is a very talented player and we are proud of his hard work and development with us. This decision to go on loan to West Bromwich Albion for the rest of this season is to support Ainsley and his growth further. He will be working at a very good club in the Premier League and we all wish him the best of luck during his time at the Hawthorns.”
Sam Allardyce's West Brom sit 19th in the Premier League ahead of Tuesday's six-pointer against Sheffield United at Bramall Lane.
10.59pm: Joe Willock joins Newcastle United on loan
And shortly after Ainsley's temporary departure was confirmed, so was Joe Willock's. Our Hale End graduate sealed a late loan to Newcastle United until the end of the season.
The England youth international, who has featured 17 times for us across all competitions this season, has moved to the Magpies to gain further first-team experience.
"I'd like to thank all the supporters for their warm welcome and messages so far," Joe told Newcastle's website.
"This is a club with a massive history that I've grown up watching and I'll work my socks off for the team. I can't wait to see everyone and be part of the Newcastle family."
Technical director Edu said: “Joe is a talented young player and an important member of our first-team squad. This can be seen in the number of appearances he has made for us in recent seasons.
"At this stage of his career, we have decided together with Joe, that it will benefit his development greatly to enjoy a loan period playing regular first-team football. We thank our counterparts at Newcastle United for their collaboration and we wish Joe all the best with his loan move.”
Steve Bruce's Newcastle United are 15th in the Premier League and host Crystal Palace at St James' Park on Tuesday night.
11.45pm - James Olayinka extends loan at Southend United
And we concluded our January transfer business by extending James Olayinka's loan with Southend United until the end of the season.
Our young midfielder has featured 16 times for the Blues this season and scored three exceptional goals.
His first was a brilliant solo effort against Boreham Wood in the Emirates FA Cup, the second was the winning goal in a 1-0 win against Scunthorpe United and a week later he found the top corner away to Mansfield Town with an exquisite finish.
The 20-year-old suffered ankle ligament damage against Grimsby Town which he is currently recovering from and making good progress with.