A question often asked by native speakers.

Why don’t you speak English?

First, I don’t usually talk in English in Japan.
I taught myself British English when I was a child.
When I was 10 to 11 years old, an Australian came over and we used to talk a lot.
But I responded to them all in Japanese.
The last time I spoke to a native speaker was when I was 20 years old, on a school trip to Hawaii.
I do email and chat with them, but I haven’t spoken English since.
When I in primary school, I ate shortbread and drank tea at snack time.
And I had a stomachache.
I didn’t know at the time that I was lactose intolerant and that tea was not good for my body.
When I knew that, I was extremely shocked to find out that I couldn’t be British.
The Hawaiians say that a lot of my English is British English, and when I relax, I say the Aussie English.
If my father memories are correct, it seems that I was the one who had informed him of the differences in the English used by his workmates coming from Australia about a year before they visited.
I had no memory of it.