https://en.wikipedia.org/wiki/Demography_of_the_United_Kingdom#Religion
Christian 42,079,417 71.58%
Muslim 1,591,126 2.71%
Hindu 558,810 0.95%
Sikh 336,149 0.57%
Jewish 266,740 0.45%
Buddhist 151,816 0.26%
Other religion 178,837 0.30%
No religion 16,221,509 25.67%
https://en.wikipedia.org/wiki/Demography_of_London
Christian 3,957,984 48.42%
Buddhist 82,026 1.00%
Hindu 411,291 5.03%
Jewish 148,602 1.82%
Muslim 1,012,823 12.39%
Sikh 126,134 1.54%
Other religion 47,970 0.59%
No religion 1,694,372 20.73%
Religion not stated 692,739 8.47%
Total 8,173,941 100.00%
Lying much, Gaz?
...and how do you know that it was non-religious people in London who didn't vote for Sadiq Khan? How many of them aren't Labour supporters who simply didn't want another Tory - Zac Goldsmith - to be elected after Boris 'Bozo The Clown' Johnson?
Did you ask all of them?