Question: What singer born in London in 1988 joined The Voice as a new judge in 2015?

Context articles: The Voice (Australia season 4)
Asia's Next Top Model (cycle 3)
The Voice of Germany (season 4)
Vietnam's Next Top Model (cycle 6)
The Voice Portugal
The X Factor (UK series 11)
Jessie J
X-Faktor (series 5)
The X Factor (UK series 8)
The Final 1 (season 2)

The fourth season of "The Voice" premiered on 28 June 2015.
 Ricky Martin and Joel Madden returned as coaches for the fourth season.
 On 13 January 2015, it was announced that Delta Goodrem would return to the panel, and new judges Jessie J and Benji Madden would join the series, replacing former judges Kylie Minogue and will.i.am.
 On 22 February 2015, it was announced that Sonia Kruger would be joining the fourth season as a co-host with Darren McMullen.
The third cycle of Asia's Next Top Model aired from March to June 2015.
 Nadya Hutagalung confirmed that she would not be returning for cycle three.
 She was replaced by Filipino model and TV personality Georgina Wilson.
 Joey Mead-King returned to the judging panel for the third time, while "Australia's Next Top Model" judge and fashion designer Alex Perry also joined the show as a new judge.
The Voice of Germany (season 4) is a German reality talent show that premiered on 9 October 2014 on ProSieben and Sat.1.
 Based on the reality singing competition "The Voice of Holland", the series was created by Dutch television producer John de Mol.
 It is part of an international series.
 Only one judge from season 3, Samu Haber, singer of the Finnish pop-rock band Sunrise Avenue was retained for season 4.
 The other three judges of season 3, Nena, The BossHoss and Max Herre were replaced.
 Nena and The BossHoss had served for the program's all three previous seasons and Herre had been a new judge in season 3.
 They were replaced by the returning judge, the Irish singer-songwriter, guitarist Rea Garvey, a judge for seasons 1 and 2 coming back after a hiatus of a year.
 Stefanie Kloß lead singer of the band Silbermond resided for the first time in the series.
 So did the two collaborating judges sitting together, the German artists Michi Beck and Smudo both part of German hip hop group Die Fantastischen Vier.
 The season was won by Charley Ann Schmutzler.
Vietnam's Next Top Model, Cycle 6 is the sixth season of "Vietnam's Next Top Model".
 It premiered on August 2, 2015 at VTV.
 For the third time, males were still featured as part of the show.
 This year, former host Phạm Thị Thanh Hằng, who hosted Cycle 4 (the first guys-and-girls season of the show), returned to fulfill her position as head judge of the panel.
 Samuel Hoàng reprised his role as a judge after Cycle 5 concluded.
 Designer Adrian Anh Tuấn was also introduced as a new judge.
 This season's theme is: Keep Moving - Không Ngừng Chuyển Động.
The Voice Portugal (A Voz de Portugal in the first season) is a Portuguese reality singing competition and local version of The Voice originally broadcast as The Voice of Holland.
 It premiered on 29 October 2011, on RTP1, with the first season finale airing on February 25, 2012, crowning Denis Filipe as the winner.
 The show came back in 2014 with its second season with new judges, a new co-host, a new show name, and new "Repórteres V" (backstage hosts).
 The winner of the second season was Rui Drummond.
 RTP1 later announced the first season of "The Voice Kids Portugal" and the third season of the main show.
 The third season premiered October 11, 2015 with new judge, Aurea.
 In its third season, the show proved to be a hit and was subsequently renewed for a fourth season, which was premiered in 2016.
The X Factor is a British television music competition to find new singing talent.
 The eleventh series began airing on ITV on 30 August 2014 and finished on 14 December 2014.
 Dermot O'Leary presented his eighth series of the main show on ITV and Sarah-Jane Crawford presented spin-off show "The Xtra Factor" on ITV2, replacing Caroline Flack and Matt Richardson.
 Louis Walsh was the only judge from series 10 to return and was joined by former judges Simon Cowell, and Cheryl Fernandez-Versini, and new judge Mel B.
 Sharon Osbourne, Gary Barlow and Nicole Scherzinger left after series 10.
 Former judge Tulisa returned as a guest judge for the final on 13 December due to Mel B being ill.
 The series also saw the lower age limit decreased from 16 to 14, as it was in series 4 and 5.
 This was Walsh's final series as a judge before returning in series 13.
 It was also the only series in which Mel B was a main judge.
 It was O'Leary's final series as presenter on the main show, as he announced on 27 March 2015 that he was leaving to pursue other projects, before returning in series 13.
 On 11 May, Crawford also confirmed via Twitter that she would leave her position as "The Xtra Factor" presenter.
Jessica Ellen Cornish (born 27 March 1988), known professionally as Jessie J, is an English singer and songwriter.
 Born and raised in London, she began her career on stage, aged 11, with a role in the West End musical "Whistle Down the Wind".
 She studied at the BRIT School before signing with Gut Records and striking a songwriting deal with Sony/ATV Music Publishing.
X-Faktor is a Hungarian television music competition to find new singing talent.
 The fifth series was broadcast on RTL Klub in 2014.
 presented his second series of "X-Faktor".
 , Gabi Tóth and Róbert Alföldi all returned to judge the talent for the second time.
 Gábor Szűcs, a new judge joined them, replacing the original judge .
The X Factor is a British television music competition to find new singing talent.
 The eighth series commenced airing on ITV on 20 August 2011 and ended on 11 December 2011.
 The winner was Little Mix, a four-piece girl group known earlier in the series as Rhythmix, consisting of members Jesy Nelson, Perrie Edwards, Leigh-Anne Pinnock, and Jade Thirlwall.
 They became the first act in the groups category to win in the UK show's history with new judge Tulisa emerging as their winning mentor.
 Dermot O'Leary presented the main show on ITV, while Caroline Flack and series 6 runner-up Olly Murs co-presented the spin-off show "The Xtra Factor" on ITV2, replacing Konnie Huq from the previous year.
 Louis Walsh returned to the judging panel and was joined by Gary Barlow, Kelly Rowland and Tulisa.
 Barlow, Rowland and Tulisa joined the panel as replacements for former judges, Simon Cowell, Dannii Minogue and Cheryl Cole.
 Series 5 winner Alexandra Burke served as a guest judge for week 4 of the live shows due to Rowland having a throat infection.
The second season of "The Final 1" premiered on MediaCorp Channel 5 on 5 July 2015.
 It is a Singaporean reality-singing competition programme created by the director of Hype Records Ken Lim.
 Taufik Batisah and Lim returned for their second season as judges, and were joined by new judge Jaclyn Victor who replaced Kit Chan.
 Chan later returned to the show as a guest judge while Victor was away for her maternity leave.
 Season one's runner-up Shaun Jansen joined the show as the host.