Change is the one constant in life. It’s inevitable.

We grow, we learn, we develop and we age.

You can see it in the lines of our faces, in the shifting, twisting, turning pathways we take, in our big decisions and little choices, in our thoughts, perspectives and dreams.

But while change affects us all, the speed with which it makes its impact is never more evident than to those of us with small children.

My son – my youngest – starts school this week.

A momentous milestone in his short existence. But with all due respect to his feelings, it’s an even bigger one in mine.

A survey of British parents carried out earlier this month found that a child’s first day at school is more significant to mum than their first word, first step or first birthday.

It’s the point where we hand them over to someone else’s safe keeping, knowing we will never really get them back.

He will experience the adjustments that come with beginnings, new starts and exciting adventures ahead.

Me, on the other hand, I am starting the long letting go.

The goodbye at the school gate is the first in the rituals of parting which pave the way to his independence.

Best friends, playdates, sleepovers, scout camp, girlfriends, teen holidays, college, gap years and university will follow. And all of it taking him further away from the place where mummy is the centre of the universe.

I know it’s inevitable. And I want him to go out there and conquer the world.

But when his little hand leaves mine and slips into the cool, calm palm of his new teacher, a little bit of me will crumble.

He will be happy in her care. She is far more qualified, experienced and infinitely nicer than I am.

But I can’t help but feel a little put out that it will be her who gets to see his gorgeous smile, listen to his hysterical jokes and control his rambunctious, irritating ways in all those daylight hours that no longer belong to me.

Of course, as he skips off to join his new class I will be bursting with pride.

But that will be accompanied with part resignation and part self-pity and a smattering of something a lot like grief.

I’ve promised myself I’m not going to cry.

I can’t. After all, this is his moment.

He wants to get stuck in, make new friends, learn to read, write his name, splash paint around and find his place in that frenzied hive of the playground.

I am looking forward to hearing all his stories when he gets home.

And truth be told, there is a part of me that is thrilled someone else will be responsible for him. I am relieved to be resigning my unpaid holiday job as children’s entertainer, referee, short-order cook.

That I will get more time to work. That I can finally get around to doing all those other things I never have time to. Pluck my eyebrows, read a book, steam clean the curtains.

All other jobs have been put to one side this week as we prepare for school. And there has been a lot to do.

Uniform to purchase, shirts with Velcro fastenings at the collar and stiff shiny shoes to break in. I’ve taught him how to fasten buttons, hang up his coat, wipe his own bottom.

It’s very difficult for him to get his head around what is about to happen.

“Will I like it there?” he asked.

“Yes absolutely,” I nodded.

“Will you be there?” he said.

“Only to drop you off and then I pick you up at the end of the day.” I replied.

“And is it just for one day?”

How do I answer that one?

Um, no actually. The true freedom of childhood is gone forever. This is the first institution many you will encounter in life as you are molded into what society believes is a model citizen. You are about to be thrown into a system where you will be expected to fall into line throughout your education and well into your career. You will be monitored and measured on your ability, effort and behaviour. From here on in it is a long march to conformity from the alphabet and times tables to mortgages and pensions, graft, pressure and responsibility – until the day you retire. And frankly for your generation that is likely to be in about 70 years time.

That’s it my boy.

“No you go every day and then you get another holiday at half term,” I said after thinking about it for a moment.

“Oh good,” he replied. “It’s getting quite boring at home.”

While his response stung, I can see that he is well and truly ready to spread his wings.

And there is far more stimulation in the hub of the school community than I can ever offer at home.

Of course I shall be among the 84% of mothers struck down with Empty Nest Syndrome once school starts.

The back to school blues will hit me when I sit down to have lunch by myself, when there is nobody there to pile unnecessary items into my Tesco trolley during the weekly shop.

I shall miss him on my daily dog walk, when I sit down for an afternoon cup of tea without a blonde head lying on my lap. I will even miss his noise, his chatter, his inane conversation, his crazy giggle.

Losing your baby to the growing up process is always going to be hard.

But for those of you going through it with me this week, we have to remember that we cannot live our own lives through our children.

The fact that we are no longer desperately needed for anything and everything is as satisfying as it is terrifying.

After all, parenthood offers us many lessons – in patience, sacrifice but ultimately, in humility.

Because the very best thing about your life as a mum or a dad is playing a part in someone else’s.

Find me on Twitter @EllenWiddup