This story was always told by my Mother as an true family story.
I was discouraged from this belief by finding it, or at least a very close approximation of it, related in the Private Eye “True Stories” series of urban myths. It is not beyond the bounds of possibility that the story originated from my Grandmothers house and,as the protagonists are dead, I suppose we will never know.
Myth or truth, the story bears retelling.

My Grandmother and Grandfather Daly lived in some luxury in the fashionable suburb of Blackrock in Cork. Their red brick Victorian detached house was on a very smart row of houses known as Ardfoyle Villas and had an extensive back garden, I would say about an acre in size. (Then again I was very little when I last saw the place)
The house was on a rise over the garden which had a vegetable garden on one side and the rest was lawn which I remember them using for croquet..
My mother was the eldest of six siblings and her brother Neil was a bit of motor bike fanatic. This incident happened in the late twenties when my mother and Uncle Neil would have been in their early twenties.

Uncle Neil, in the pursuit of motor bike perfection, was taking a bike to pieces in the back yard of Ardfoyle. Having stripped it down he was engaged in cleaning off the various bits with cotton waste dipped in petrol when my grandmother got him to clean up the mess as she was having visitors around to play croquet on the lawn. Expediency being the better course he decided to flush the petrol soaked bits of waste down the outside toilet which was also in the yard.
Shortly after that , the gardener, seeing that my grandmother would be occupied with the croquet, decided to take advantage of the break to use the same toilet and also smoke a pipeful of tobacco.
The gardener arranged himself luxuriously in the toilet, trousers around his ankles, for his session as my Grandmother entertained her guests on the lawn sloping down from the yard. He lit his pipe, and , as always flicked the match down the toilet.
There was an immediate explosion and the gardener was catapulted out of the toilet, trousers still around his ankles, right into the middle of my grandmothers croquet party.
He lay there, stunned and totally mystified and looked up at my Grandmother and said;
“ Jaysus Mam !, it must have been something I et.”

That was the story as my mother told it.
It has since gathered various alternative endings.
One that was told to me by a cousin also managed to find its way into the Private Eye version.

The gardener who was shook and –I have no doubt burned- by the explosion was brought upstairs in the house to be attended to.
Deciding that the nature of the injuries were beyond their first aid skills the decision was made to call an ambulance.
This arriving in due course the gardener was being carried down the stairs by the two ambulance men on a stretcher (lying on his front one assumes)
One of the bearers asked what happened, on being told he collapsed in hysterical laughter, let go of his side of the stretcher, and let the poor unfortunate gardener roll off, and down the stairs thereby managing to add to his injuries by breaking his leg.

That ending must definitely be regarded as apochriphal.
My mother, who I have never had cause to doubt , told the first half as the gospel truth.