Has anyone tried to attack you while you've been at work recently? Probably not, but a news story today suggests that it happened to Terry Alderton during a gig this week. The Essex stand-up was doing a charity gig at the Prince William of Gloucester Barracks in Grantham when, according to Chortle, someone jumped onstage. In the ensuing fracas it sounds as if Alderton was the winner, tweeting later that his opponent "went down like a wet rag."

This does not usually happen to people trying to earn their living, although I have felt like thumping a few bankers lately. There have, however, been a couple of incidents with goalkeepers recently. Alderton, coincidentally, is an ex-goalie, so maybe there is a connection there. But, in fairness, most people have a right not expect to be interrupted like this while they are doing their job.

There is a suggestion that alcohol may have played its part in the man deciding to get in on the act. Alderton does do a lot of strange banter with the audience. Maybe a surreal put-down was mistaken for a polite invitation. When I saw Alderton at the Altitude Festival recently he also had an enthusiastic, possibly well-refreshed, supporter who ended up joining in, though that time Alderton invited him onstage before carrying him offstage. 

Alderton is not alone. Jim Jefferies famously had a too-close enounter at the Comedy Store a few years ago. Alcohol reduces fans' inhibitions, but even without the liquid lubricant they can have a habit of getting a little too involved. At The Boy With Tape On his Face's West End show last December the silent star invited a fan onstage to put work clothes over his own clothes and when Tom Jones' You Can Leave Your Hat On from The Full Monty started to play the sporting fan picked up the cue and correctly started to remove the prop clothes. Except that he was loving the attention so much he looked like he was about to remove his own clothes too. Tape Boy quickly intervened. 

A few months earlier Ross Noble, who usually has a brilliant rapport with his demographic, got into a sticky situation at the Hammersmith Apollo when he asked a pair of fans close to the front to move seats slightly so that a nearby couple could have an "upgrade". The fans wanted to stay put. One gave Noble the finger, and a stand-off ensued. Security guards loomed and what started off as a jovial exchange nearly turned messy.

There is a car crash frisson when this happens in live comedy, but it rarely happens in mainstream theatre. If anything it is usually the actor who loses their rag there. The late Richard Griffiths was so infuriated by mobiles ringing he halted dramas to remonstrate with phone abusers, but unscripted banter between punter and performer is much more common in stand-up. Sarah Millican broke away from her usual smut to ask a fan to stop filming her set at Wolverhampton Civic Hall.

This is just another way in which the dividing line between performer and punter seems to be becoming increasingly blurred. It may be my imagination but I'm sure heckling is increasing. Maybe audiences are now so used to shouting at the screen when they are watching Live at the Apollo that they think they can do the same thing at gigs - usually prompting the response "this is not the telly, I can actually hear you."

But this blurring of lines also coincides with the rise in "immersive" comedy shows where the audience really does become part of the act. Adam Riches and Dr Brown have both won the Foster's Comedy Award in Edinburgh in consecutive years with shows where the public ended up being co-stars. You could almost feel the collective unclenching of buttocks as Brown and Riches picked someone else to be their "victim" for the night.

Maybe the audience member at Terry Alderton's gig was confused and thought he was supposed to get up onstage. I should imagine Terry Alderton has seen a lot in his time, but it must have still been a shock to find his stand-up gig turning into an impromptu WWF bout. I bet Richard Griffiths never had that problem.