From the photographer's website:
"Today's liturgy is particularly evocative because it is marked by the symbol of light. The solemn procession with candles which you made at the beginning of the celebration points to Christ, the true light of the world who shines in the night of history and illumines every seeker of the truth." - Pope Benedict XVI
"2 February is the feast of the Presentation, also known as Candlemas because of the procession with blessed candles.
"The mosaics in the Lady Chapel of Westminster Cathedral, of which this is a detail, began in 1930, and lasted 5 years, under the direction of Basil Cary-Elwes to designs by Gilbert Pownall.