Ultravox, Hammersmith Apollo

Now I think I've seen it all. After a storming two-hour set Ultravox returned to the stage for a celebratory twin-pronged past-meets-present encore of "Dancing with Tears in My Eyes" and "Contact". At the very end, during a touching, soft-spoken moment, a female fan in an animal mask clambered onstage and appeared to drop a bowl of greeny-yellow gunk, possibly custard, on Midge Ure's head.

The woman was bundled off and a towel cleaned up the dapper vocalist, but the crude incident was in breathtakingly stark contrast to the glistening gig that had preceded it.

Ultravox was always an intriguing band, fronted initially by John Foxx and then by versatile all-rounder Midge Ure, who had already tasted varying degrees of success with Slik, Rich Kids and Visage. In 1981 they finally broke big, finding themselves unexpectedly cool and part of the New Romantic movement and the plugged-in synthesiser generation alongside Gary Numan, The Human League and Heaven 17. The hit single "Vienna" cemented their reputation as purveyors of classy pop, even if it only reached number two in the charts, pipped at the post by Joe Dolce's "Shaddap You Face".

For every fondly remembered Eighties single there was a fiendishly effective new track

The band inevitably fell out of fashion and eventually split. A largely different line-up existed for a while in the 1990s, then in 2008 Ure, bassist Chris Cross, drummer Warren Cann and keyboard/violinist Billy Currie reconvened. Their 11th studio album, Brilliant, garnered positive reviews earlier this year. This gig was a canny cocktail of the old and the new. For every fondly remembered Eighties single, "Sleepwalk", "Passing Strangers", "Love's Great Adventure", there was a fiendishly effective new track, even if some wore their influences a little too readily. "Change" featured a spine-tingling Kraftwerk homage, "Rise" had the infectious synth rhythm of OMD.

The mood of the night evolved as the epic 27-song set went on. The first half showcased the gloomier, angstier side of Ultravox, with monochrome Expressionist movies projected behind the unfussy set during "Mr X" and the band being bathed in a navy light during "Visions in Blue". There was something distant about the quartet, and not just because there was minimal chat and they stood an unusually long way from the edge of the stage. Only brief walkabouts from Billy Currie, who prompted huge cheers whenever he picked up his violin, and from Chris Cross as he shared the vocals on "Reap the Wild Wind", offered reassurance that the production budget was able to stretch to an extension lead.

After the interval, however, the gig quickly went up through the gears with a run of songs that foregrounded Ure's pint-sized axe hero pedigree – lest we forget, the Zelig of the Les Paul also played briefly with Thin Lizzy. In the middle of this high-energy romp, following the track "Astradyne", complete with extended ska riff, the lights dimmed and with a minimum of alarums and excursions they rolled out "Vienna" to much clicking of iPhones and much tutting of security staff. Ure's operatic vocals were bullseye-accurate on a song which is essentially a post-punk "Bohemian Rhapsody", right down to the nonsense lyrics and dramatic changes of pace. And then the moment was over and Ure picked up his guitar again and got back to hammering out those shimmering solos and encouraging the audience to clap and dance.

After a deafening "All Stood Still" and the rip-roaringly biblical "Hymn" the band disappeared, before returning for that fateful encore. It had all been going so well. The last time I saw anything like this was when a fan got onstage and kicked The Fall's Mark E Smith. Tonight's incident was less violent, but so out of context just as shocking. Ure appeared to keep calm and carry on like the trouper he is and later jokily tweeted that he was concerned it might have had sugar and carbs because he is on a diet. But many who saw what happened left the venue slightly stunned. Others who heard about it from friends started cracking jokes on Twitter about Viennetta, dubbing the incident Triflegate and hoping the flan-flinger gets her just desserts. Let's just hope Midge Ure can see the funny side and it does not stop him doing what he clearly loves. 

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Watch Midge Ure discuss his favourite track from Brilliant