Still smiling, he stuffed it eagerly into his mouth.
Moments later, he started coughing and then the nightmare began. I froze in horror as he struggled to breath and his lips turned blue.
Thank heaven there was a mum there who happened to be a GP. She grabbed Lucas, then forcefully slammed him on the back a couple of times until the offending biscuit dislodged itself from his throat and flew out of his mouth across the floor (thank you, the wonderful Dr Nicola Mogford!)
I often go cold when I think back to that moment...would I have been able to save Lucas had we been alone?
Immediately after the horrible event I - naturally - signed up to attend a course to learn First Aid.
At least... I intended to.
I read some first aid books, I looked up some courses online.
I thought about it a lot.
But, okay...I'm ashamed to admit it. I never actually make that course booking.
And I have absolutely no excuses as to why not. Other than the usual lame: Time rolled on. Life took over.
It's only now, an embarrassing six years later, that I'm finally urged to bite the bullet when I hear about the new First Aid Challenge campaign launched by The British Red Cross - running until the end of the year - which aims to get thousands of parents across the UK to learn first aid skills and to feel confident enough to use them in any crisis.
Their challenge to the public comes in response to research figures which show that two thirds of parents don't feel equipped with the knowledge to deal with their worse emergency fears – such as choking, treating an unconscious baby or child and meningitis – or worry they'll do something wrong if they do attempt to deal with such an emergency.
With these kinds of figures, why aren't we all clamouring at the doors of the Red Cross to sign up for a first aid course as soon as the little blue line shows up on our pregnancy tests?
Joe Mulligan, British Red Cross head of first aid education tries to explain why:
"We all have good intentions and a whole list of things that we mean to get around to doing but somehow some of these things never make it to the top of the list," he tells me.
People also think that first aid is somehow complicated. This, combined with the fact that, as parents, we don't want to think about some accident happening to our kids, hampers us from making that step of booking a course and learning first aid.
I sign up for a Saturday five hour course in First Aid for Baby and Child at my local Red Cross Centre. (There's also the option to split the course over two consecutive evenings).
There are eight of us on the course that day. I'm very impressed (and put to shame) to see two (obviously very organised and responsible) pregnant first-time mums with their partners (both of whom I learn have studied First Aid at their places of work before now and who felt they needed more specialist and specific knowledge on how to treat babies).
There's also a mum who works as a nanny and is topping up her first aid training and another mum of three small children who has studied first aid several years before when she worked as a lifeguard.
So apart from myself, there's just one other mother who hasn't formally learned any first aid before. She has a two year old and another on the way and explains that – as her husband works away– she's left on her own with her child a lot of the time, so felt she needed to learn some skills just in case.
She's embarrassed that it's taken her two years to sign up for the course. Cue awkward cough as I inwardly debate whether I should knock a few years off my two boys' real ages, just to make myself look a little better....
The following hours are spent with our expert trainer teaching us how to cope with all sorts of emergency – from burns and choking, to severe allergic reactions, head injuries, raised temperatures, bleeding, an unconscious child and more.
We get to practise CPR on baby and child dummies, we get to put each other into the recovery position, we watch videos, we answer and ask questions and amongst all the learning, we have a bit of a laugh as we struggle to find each other's pulses and make a mess out of attempting to turn a square piece of fabric into a sling (it's a skill some of us just aren't cut out for!).
At the end of the day, I feel a lot better equipped to deal with any unwanted emergency. Reading something in a first aid manual is one thing – but practising CPR on a dummy with an expert trainer on hand to tell you just how hard you have to press on the chest for example – is another.
We all leave the course hoping we'll never need to use our skills, but more confident that we'd be able to handle a health crisis without panicking.
Naturally, I now wonder why I didn't find the time to do this years ago – and I'd urge every parent out there to give up just a few hours to equip themselves with these easy to learn skills.
(Hark at me being so holier than thou now that I've finally done it ....) But honestly. It's just a few hours out of your life that might – just might – come in handy one day. Put bluntly: It could save a life.
Exactly a week after the course, I was watching my elder son play football when a dad at the pitchside collapsed. I won't pretend I was first on the scene – thankfully there was a far more experienced first aider who rushed over to do that. But it felt empowering to know that, had I been alone with that man when he keeled over, I'd have known what to do before the emergency services arrived (keeping his airways clear and placing him in the recovery position if he was unconscious for example).
If you're feeling at all inspired, I'd encourage you to look up the Red Cross First Aid Challenge website (see below). There are three challenges you can sign up to:
Challenge One: Learn online. Spend just one minute watching a short video to learn how to help a child who's choking (or take 25 minutes to watch videos which will teach you what to do in 20 different first-aid situations). If you prefer you can get information sent to you in bite-size chunks for learning.
Challenge Two: Enrol onto a local first-aid for baby and child course and get £5 off the regular price (courses normally cost from £37.50).
Challenge Three: Sign up to download a letter calling on your headteacher to include first aid education for children at your school.
More information: www.redcross.org.uk/firstaidchallenge
More on Parentdish: Does your child know what to do in an emergency?