Follow Oliver on: The UK blue-chip index continues to slip back from key level 9.39am: Avast wanted after update Avast PLC (LON:AVST) is one of those companies you would not necessarily immediately think of as a member of the UK's leading index. But it certainly is, and not only that, at the moment it is leading the way. Its shares are up 3.16% or 14.9p at 486.5p after a positive first quarter trading update. The cybersecurity business said revenues had risen 10.5% at actual exchange rates and adjusted earnings rose 10.3% to $133.7mln. It expects full year revenues to grow at the top end of the 6% to 8% guidance range following the disposal of its Family Safety mobile business on 16 April. With investment in R&D and marketing, margins are expected to remain broadly flat.