Japanese maple tree trunk split

Can anyone please give me some idea as to why my Acer Palmatum tree trunk all of a sudden has split like this? I've had the tree for a good 10+ years and went to check on it yesterday and noticed the trunk has a fairly deep split in it. First time I've seen this.
The tree is in a wooden container and has been outside in the harsh winter, not sure if that could have something to do with it? I'm concerned it's damaged beyond repair.... Anyone else have experience with this or know what could have damaged it? And is it likely to survive?
The tree is in a wooden container and has been outside in the harsh winter, not sure if that could have something to do with it? I'm concerned it's damaged beyond repair.... Anyone else have experience with this or know what could have damaged it? And is it likely to survive?

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If you live in Derbyshire, as I do.