The media are blaming it on Brexit, standard reaction right now. Bad times whatever the reason.
You never know, in 3 years time the UK might have a more favourable trade deal with Japan than the EU does.
That cannot happen. A clause in the Japan-EU FTA prohibits Japan form making a deal better with a third country than what it has with the EU, unless the EU agrees. This is a pretty standard mechanism in modern trade deals and is the reason why the claims made by our lying politicians that we can do better on our own with better deals are nothing but bare faced lies.