Warner earned a PhD at University College London for research investigating single molecule spintronics.
[2][3] Warner was a postdoctoral research fellow in quantum physics at the centre for nanotechnology at University College London.
[4][5][6] He left to join ASI Data Science (now Faculty),[7] a company founded by his brother Marc Warner in 2014, where he is now[when?]
[2][8] Warner was a key figure in the computer modelling used by Vote Leave's successful 2016 referendum campaign.
[9][10] Warner was a member of the Scientific Advisory Group for Emergencies (SAGE) during the COVID-19 pandemic, with Cummings and 21 others.