When I was a young boy, perhaps 10, I wore a lamb’s knuckle to school for one week, on a chain around my neck.

I discovered the knuckle in our Sunday lamb roast one evening and suggested to my father that I would like to wear it to school. Rather than discourage this suggestion my father boiled it down until it was clean and gristle free, drilled a hole in it, and gave it to me on a silver chain.

I distinctly remember it bulging awkwardly underneath my t-shirt like an untreated goiter. I kept it secluded in this fashion during class time and then allowed it to dangle free during recess and lunch, a caveman trinket swinging and hitting me in the chin while I competed furiously at hand-ball, or wall-ball, or dodge-ball, or some other ball related activity.

It only took until the first afternoon for a teacher to ask me about it: “Is that a special bone of some sort? Did you get it on holiday?” No, I answered, I found it in our lamb roast last Sunday. The teacher had no further questions for me at that time but presumably went to the staff room to discuss my adornment in an incredulous tone.

If I am being honest my father had done an imperfect job in boiling down the gristle. Some chewy looking particles remained; and even a rudimentary inspection would confirm my jewel was more likely to be table scrap than a petrified dinosaur molar, or something else of actual or sentimental value.

The children loved it. My hand-ball game was on fire, buoyed by the confidence that only the adulation of a group of primary school children can give you. Rumours circulated about how and why I had come upon this beast’s knuckle bone, and what captivating tale there must be behind its acquisition. I, however, did not feed these rumours. Throughout this brief but memorable period I was always completely honest about the entire story; we usually have a leg of lamb on a Sunday, I had asked my dad whether I could gnaw on the leg bone, he had said yes, I had sucked on it for a while, spat out the knuckle, liked the look of it, asked my dad whether I could wear it on a chain, he said yes and then enabled my request.

I was oblivious to the opportunity for fabricated tales of heroism with which I had been presented, and seemingly oblivious to the fact that the truth was, well, a little bit weird.

Anyway, by Thursday the spots of remaining gristle had become a little funky and my teacher, who had likely been discussing and planning her next approach since the Monday, gently asked me again to recount the story, confirmed whether or not the bone had any sort of sentimental value, not really, and then suggested that perhaps I might consider whether it needed to come back to school with me on Monday. It didn’t.

I am not sure where the knuckle ended up. I continued to wear the chain for a little while but quite soon that too disappeared and the incident drifted over the years into the realms of anecdote.

Today I believe I experienced some of what my father did all those years ago that lead him to what objectively might be considered a reasonably odd decision.

Exhausted and hungry after an exhilarating Gymbaroo today, Milo and I shared a lamb shank for lunch, which he devoured aggressively. At the conclusion of the meal he reached his little arms forward toward the bone, picked clean but still tasty looking. I did what any loving parent would do and handed it to him. The focused joy and systematic gnawing I witnessed was heart-warming. It looked like a small dinosaur bone in his little hands as he waved it around and sucked furiously on its knuckled end.

It was only when he really started to pull with his teeth at the bits of fatty gristle that remained attached to the bone, with success, that I removed the impressive shank from his firm grasp. The forlorn look on his face and his little lips still smacking together were heart breaking, and I know at that moment had he asked me to fashion it into a belt buckle, or a head-piece or a hair-comb I would have said yes immediately and put the kettle on.

 Shankin’

Today was our penultimate Gymbaroo together. Invigorated by Valdis’ words and gestures the previous afternoon Milo looked relaxed, peering out the window at birds and aeroplanes on the drive over. As we arrived Felix looked up from his mop and gave us a gentle smile and encouraging nod, then returned to disinfecting the equipment. I thought I identified a hint of concern as he quickly returned to his work.

There had been ‘chatter’ all week on the Gymbaroo forums that something ‘big’ was planned for this session. We had caught phrases like ‘tube of terror’, ‘the strangler’, ‘tubenado’ and ‘tube the noob’. The previous afternoon Valdis had also briefly looked up from his Kandy Krush Saga and grunted something rather cryptic at us while Milo was scaling Grandma’s Cottage; “I hope Milo isn’t afraid of the dark”. I looked up quickly for an explanation but his head was already down again, only the coiffed badger could be seen.

We had dismissed it at the time as the ravings of a brain over-stimulated by animated Kandy but now, standing in the gym room for the second last time together, it was soberingly clear

Snaking out before us was the longest, most intimidating tunnel Milo or I had ever seen; an ominous deep red in colour it was at least twice as long as any Milo had ever attempted. It curled left and right, into valleys and up over yellow foam triangles that looked like immense pieces of cheese discarded by a giant mouse. We peered into it together, and we could not see the exit.

Milo went through the motions during the stretching, dancing, massaging, odd rhyming, upside-downing. Milo predictably crushed a limp-wristed opposition in the wheelbarrow but I could tell he derived no pleasure from this. His mind was on other things.

Uncomfortably soon we heard the words “free time in the gym now”. The usual exuberance was absent. None of the babies moved toward the gymnasium. Several feigned a renewed interest in the bucket of assorted plastic ducks, trying to convince their parents they wanted to explore it further, one crawled back to the pile of pantyhose filled with rattly balls and pretended it was the greatest toy he had yet encountered. One of the smaller kids simply began to cry.

One by one the babies were scooped up by their parents and taken into the gym, deposited here and there to shimmy unsteadily along beams, bounce listlessly on the mini-tramp, pull at the robo-turtle’s leg and recline in the sheepskin lined plastic shell. Milo and I took up a position alongside the rolling wedge which offered a good vantage point of the demon tunnel’s gaping mouth.

Milly, a plucky, smiley baby who has always competed well and is near the head of the class in terms of walking progress, was deposited directly at the cavern’s entrance. Milly’s mother then took a tambourine to the exit and attempted to coax her through. Her voice sounded like a distant echo and the tambourine a tinny whisper. Milly’s smile slipped away for the first time in weeks as she edged into the darkness and out of view.

All baby eyes were on Milly, breath collectively held. The tunnel vibrated slightly to indicate Milly’s process, which was slow and stuttering. After what felt a baby lifetime Milly re-emerged from the entrance, wide-eyed and unsmiling. Milly’s mother arrived swiftly and took her to the horizontal ladder to recuperate.

One by one we watched babies confront this challenge, many could not even be coaxed to begin the journey, even when encouraged by the tambourine with streamers attached. Those that did venture inside lasted only moments before scampering back to freedom. Lennox had been notable in his absence at the mouth of this fiendish tube, executing impressive routines on the lower level apparatus around the room.

Eventually Milo burst out of my arms, through the short wooden culvert which marked the entrance to the beast and disappeared out of view. I scurried alongside the tunnel as it bulged and shook with Milo’s progress, attempting to beat him to the exit. He took the corners swiftly and moved up and down the hills and valleys as if he were back at Valdis’ gym, clawing his way over the Plain of Pyramids. I heard him growling and yelping with determination as he plunged through the dark.

I traversed the tunnel and slid onto my stomach, desperate to peer into the abyss and locate my son. All was silent. The tunnel was still.

Just as I was considering whether I could squeeze my shoulders into the tunnel, and how embarrassing it would be to have the Gymbaroo panel cut me out of it, Milo’s smiling face popped around the corner and he ploughed toward me with his jaunty crawling style. I waved the dodecahedron at Milo to encourage him the last few metres but all of a sudden he paused.

It was then I noticed Lennox at my left shoulder, crawling past me with his eyes on Milo and one hand on the dodecahedron. Lennox, at great pace, covered the metres between them swiftly and they met for the first time, face to face, in the red tinged darkness of the devil’s throat.

The two great rivals then awkwardly shuffled around each other as if they were square dancing, aligned themselves and crawled happily out together, chatting in conflicting languages that neither understood.

Lennox’s father and I scooped up our respective champions and chatted comfortably about the difficulties of executing Swim School alone, the complexities of managing Gymbaroo expectations and how easy it is to not shave for days at a time as a stay-at-home dad.

The parachute and farewell song drifted past us, Milo grinning and satisfied at his ability to overcome his apprehension of the tunnel, and of Lennox. Perhaps these two great rivals now have the foundation of a great friendship, as they both prepare for their graduation to the ‘Fairy Penguins’ in the coming weeks. Or perhaps they were simply caught in a moment. Time will tell.

So we finish the story where we began, two satisfied lads eating slow cooked lamb shank together, and dreaming of the future.

• Total length of devil’s throat (m) – 6
• Number of Gymbaroo sessions remaining in Part One – 1
• Pairs of jean shorts fashioned out of worn-out jeans – 0
• Days since last shave – 6