"I suppose we'll have to sit separately," may not sound like a particularly threatening turn of phrase.

But, when delivered by a 13-year-old girl who wants to sit with her teenage friend but (due to the powers that be having recognised that it's the Easter holidays and accordingly cut the number of carriages on most of the trains) cannot find two seats together - and you are occupying the double seat she and friend had their eye on, it certainly makes you squirm uncomfortably.

I suppose I could have moved and sat in the aisle facing backwards but I reasoned: A) I'd been hard at work all day, whereas they'd been shopping, B) I'd paid a small fortune for the pleasure of travelling up before nine in the morning, whereas they were no doubt using a lovely cheap travel card, C) I got here in plenty of time to secure a window seat, facing forward, whereas they'd left it to the last minute and D) didn't they know they were lucky to get a seat at all and if they didn't sit down - separately - soon all the remaining seats would be gone?

So, I ignored girl one's threatening plea to move and stayed put. She then sat in available seat next to me while her friend sat in the group of seats behind. Shortly after, girl one's mobile phone bleeped, alerting her to text message - which I happened to notice read RUOK - followed by irritating sad face sign :-( . GR8 (great) she messaged back, signalling the start of a conversation with friend, with whom she'd been denied the pleasure of sitting, which lasted until Gatwick Airport - when I could bare the incessant beeping no longer.

Girl one seemed to have programmed her phones dialling to tone to loudest possible setting and after the start of their conversation, when they at least had the good sense to use abbreviations, they began tapping out full blown sentences.

WADYA want 2 do 2nite? (beep, beep, beep, beep, beep, beep, beep etc. etc) WAN2 C Luke (beep, beep, beep, beep, etc. etc.)

OK where shall we meet (beep, beep)

Outside the 24-hour supermarket (beep, beep, bloody beep ...)

Have never quite understood the point of text messages, since in the time it takes to bleep them out you could have left a dozen spoken messages - but seem to be very popular, especially with teenage girls who have already spent all day in each other's company.

These messages seemed particularly inane and loud. So I gave in.

"All right," I barked to girl one. "You can sit with your friend. I'll swap seats."

And I gestured for girl two to get up and join her friend. They seemed happy enough, though the beeping continued, and after a few minutes own phone signalled to me that it had received a text message.

It was one of those irritating smiley faces :-) .

"Anything interesting?" said blond athletic man from Hassocks who in changing seats with girl two I had fortuitously ended up sitting opposite.

"Just one of those stupid irritating smiley faces," I replied, venting my anger on the two bleeping girls on a perfectly innocuous text message.

"Right..." said Hassocks looking subdued and it only dawned on me, when he had left the train at Hassocks that perhaps the annoying smiley face was in fact a charming flirtatious message from him....