Between 515 competitors, over 38,000 Modern cards were registered for this event. Here is the breakdown of the most popular cards (other than basic lands) in the format. Let's start at the top.

Modern is a fast format, so you have to be mana-efficient. Indeed, the 8 most-played non-land cards were all one-mana spells. This helps explain why Chalice of the Void is so powerful in the Modern format right now.

Surgical Extraction, Path to Exile, Nature's Claim, and Lightning Bolt are all hyper-efficient answers. Ancient Stirrings, Opt, Faithless Looting, and Serum Visions are the most-played card selection spells.

The next part of the list contains half a Tron deck, which makes sense because it was the most popular Modern archetype here in London.

Also found above are Damping Sphere and Field of Ruin, which are good ways to slow down the Tron deck. It's nice that every deck can play them, regardless of color.

Below you can find the rest of the bunch. The most-played Ravnica Allegiance cards were Deputy of Detention, Skewer the Critics, Kaya, Orzhov Usurper, Light Up the Stage, and Prime Speaker Vannifar, in that order.