Some 8,000 youth attended the sold-out Flame 2019 event at Wembley Arena on Saturday night, where the main theme was "significance".
Addressing them, the Primate of All Ireland, Archbishop Eamon Martin said: "You, my young friends, are in the heart of God and in the heart of the Church.
"You are personally called to holiness".
Organisers had hoped to offer a "fresh depth of perspective" for youngster obsessing over sites like Instagram and Snapchat for affirmation, by highlighting how they reflect the image of God.
This is what 8,000 young people adoring Jesus in the Blessed Sacrament sounds like...beautiful silence!! highlight of the day! pic.twitter.com/NvA4AbvLy4— Flame (@FlameCongress) March 2, 2019
The Canadian philosopher Jean Vanier and the Archbishop of Westminster Cardinal Vincent Nichols also took to the stage of Flame 2019.
Worship was led by artists including Tim Hughes and Guvna, while the line-up also included Premier Gospel's Ibe Giantkiller and Premier Praise presenter Candice McKenzie.
Flame is organised by the Catholic Youth Ministry Federation (CYMFED).
There were also live art installations exploring the "significance" theme and a drama by the Christian drama group RISE Theatre.
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