Where's Aikido Phil when you need him?

Day 35, February 4, 0.25 am - I found myself wishing I were Aikido Phil the other day. Or, at the very least, that I'd had him by my side.
Aikido Phil, for the uninitiated, is just that - Phil who teaches Aikido in Brighton. He's fit and fearless. His New Year resolution is to get into boxing as well.
I'm Head Sloth, unfit and as brave as a snake with a yellow underside.
So there I was, in the Tube late at night, when wild-eyed Man A for no apparent reason takes a sudden dislike to bespectacled, studious-looking Man B and begins hitting him.
This, of course, is where Phil would have moved in, quietly and calmly defusing things with i) a few quiet words of warning or, failing that ii) a few quickt Aikido blows to the head which would have rendered Man A unconcious.
But Phil is not there, just me and my knocking knees. Man A punches Man B again and I ponder, along the lines of:
Reasons to take action - Man B looks like he could do with a little help/it's the right thing to do/nobdy else seems to be reacting/how would I feel if I'd had the misfortune to be bespectacled or remotely studious-looing?
Reasons not to take action - Man A might have a knife and is, incidentally, young and fitter than I ever was/I've damaged my ankle following an argument with a factory gate and would not be much help to Man B even if I wanted to/I'm a committed coward.
And while I prevaricate an elderly gent who looks a more wrinkled and significantly less fit than me (which is saying something) charges into the fray, kicks Man A, brands him a good-for-nothing bully and chases him off.
There is not a knife to be seen and I go all the way home with my tail between my legs.
And I think: "I wish one of my resolutions had involved Aikido or boxing or bravery."
But it didn't. My first resolution involves losing weight and my second, even more uselessly, involves learning the keyboard.
If I'd had my keyboard with me, I suppose I might have used it to hit Man A over the head.
Or, if my lack of courage had not even permitted that, I could at least have tried giving him a headache with an erratic, error-strewn rendition of "Twinkle Twinkle Little Star."