A tech firm putting puzzles on a billboard at a train station in the capital knows its target in the war on talent

An outdoor poster at a train station doesn’t, at first glance, seem the most obvious way for a fast-growing internet company that specialises in online communication to advertise.

Intercom has just raised $35 million in its second investment round since the start of the year. It has more than 7,000 clients paying to use its platform to interact with their own customers. It’s refining that product at pace and also is in the ...