Mobile accounted for 51% of UK digital ad spend in 2018

"IAB UK, the trade association for digital advertising, has today announced the results of the latest IAB UK and PwC Digital Adspend study, which reveals UK advertisers spent £13.44billion on digital advertising in 2018.
The total ad spend figure is a 15 percent year-on-year increase and demonstrates continued confidence in the power of digital advertising.
For the first time ever, ad spend on smartphones has exceeded desktop accounting for 51 percent of the total spend, up from 45 percent in 2017. This is a year-on-year increase of £1.65bn.
These latest figures show that advertising spend now better reflects consumer behaviour, with recent UKOM audience data showing that people spend two thirds of their online time on smartphone1.
Beyond mobile, an additional driver of growth continues to be video, which accounts for 44 percent of the total display market. For the second year running, outstream (which includes social in-feed video) has exceeded pre-roll video2, accounting for 57 percent of all video advertising."
Source:  Press release from IAB UK, using data from the IAB & PwC, 24th April 2019