It is only when you learn more that you realise how little you knew. So it is with rugby union now that I've seen a bit of it close up from the inside. It used to be I'd be happy to hold my own with anyone, sounding forth about who's good, who's crap, who made a difference, who should never have been allowed to wear the shirt, writes Alastair Campbell.

Now I mull over my new-found knowledge, reflect on how much more there must be I still don't know, and never will, and I think to myself 'who were you ever to have voiced an opinion on anything?' But then one of the players asks me what the Dutch referendum result means for Britain, and I think, 'horses for courses'. We go via Holland to Britain to America to the threats and opportunities of the Chinese economy, and suddenly I feel emboldened again. I have views, and some knowledge and experience and though I may not know everything, I know enough to more than get by, and they nod and say 'that's interesting' and then get back to rugby talk. At which point I am happy to sit back and absorb from superior beings.

It was sitting next to Lions coach Ian McGeechan on the team coach that made me realise how ignorant I was. He had on his lap a series of what looked like war plans. There were numbers and lines, some joined up, some dotted. There were arrows shooting off in various directions, often crossing each other. There were little groups of dots being moved by pencil towards each other. There were code names written in the margins. I have kept a few secrets in my time and shall keep these. But as Ian explained what his various doodles meant, it dawned on me that when I had been going round telling the media that this was the best prepared Lions tour ever, and that the pace of change was forcing the game to advance and coaches to adapt, it was all true.

Rugby has a mass following in certain parts of the world but not, the experts will tell you, a mass understanding. Most people still have the basic view that you put five big, strong blokes up front, three big strong and faster blokes at the back of them, then a little bloke who gets the ball out to a set of blokes who are faster and smaller than the ones up front and who try to get the ball over the line, after which one of the smaller, faster ones tries to kick it over the crossbar between the posts. Meanwhile, the other side have the same set up and whoever crosses the line and gets the ball over the bar most is the winner. Then they shake hands, forget any fisticuffs that happened out there and go off for a drink together. Okay, that is an over simplification but it's enough to get most people by.

Yet not only am I now confronted by Ian's doodles, but I see the big, strong ones endlessly practising lineouts indoors without a ball and I realise there is a lot more to this than jumping. Then I see them sitting round looking at laptops and making sure they all understand the codes and I realise the preparation for a big match has all the hallmarks of a preparation for battle.

And then I wonder: is football as complicated and sophisticated as this? Have I seen hundreds and hundreds of Burnley matches without actually realising what the hell is going on? And does it matter? So long as supporters enjoy what they see, surely that is okay?

But then I think how much more I enjoyed the Lions' match against the Bay of Plenty armed with my modicum of extra knowledge and I wonder, could I have enjoyed my sufferings and exhilaration at Burnley even more?

I escape to the gym, thinking that having run a bit and completed a triathlon, at least I know a thing or two about keeping fit. Wrong again. In comes Phil Pask, Lions medic, Sheffield Wednesday fan and fitness fanatic, who is working out with Mal O'Kelly, this a few days before the lock had to bow out due to injury. As I trip along at 12.5 kph on the treadmill, they go through a series of bike exercises, squats, weights and press ups that has sweat dripping without cease from their noses.

I get off the treadmill and start to lift a few weights, at which point Eddie O'Sullivan walks in and lifts weights that make mine look like pieces of fruit. Then in comes another trainer who tells me I'm doing them all wrong anyway and for good measure Pask tells me I didn't stay long enough on the treadmill for it to have had any lasting benefit.

So now I have a proper weights programme (still a fraction of what Eddie is lifting) and I'm trying to get back into the habit of longer runs which was disrupted by the general election campaign and which I have struggled to revive out in New Zealand.

Meantime, I have learned that my diet is wrong, I eat at the wrong times, I don't drink enough water, I don't sleep enough, my sit ups are hopeless and years of not stretching before and after runs means I am more prone to injury. So I say - 'look, I'm twice the age of some of these guys, I'm a charity runner and I'm never going to be an elite sportsman and so it doesn't matter'.

But deep down, I know it does. Because if I can learn how little I know, I can get better as well as older, or at least decline more slowly than I might. So I pretend to be unfazed by the advice that comes along, then store it away. So when Richard Hill and Tom Shanklin head off for their five- minute ice bath, and tell me if I really want to know what elite sport is like I should try one, I laugh and shake my head. Then I go upstairs for a cold bath, a kind of warm up for the real thing which I might well try one day, provided nobody is watching and Hill can't carry out his threat to get a photographer along.

Later, Scottish number eight Simon Taylor asks me what it's like to run a marathon. He says he doubts any of the players could do a sub-four hour marathon because they're built for bursts not long-distance endurance. Suddenly, I feel better than an international athlete after an ice bath, and I tell Donncha O'Callaghan if only he ate, slept, drank, trained and thought like me, he could run a marathon. He looks at me in pity and goes back to learning his lineout calls.