This may sound ridiculous, but you should check this. Now that the UK is no longer in the EU, there are more stringent rules on passport validity than before (and Portugal is one of the strictest enforcers) and as of some time in 2023, it is planned that all non-EU citizens (including UK citizens) will need a visa-waiver to travel to the EU.
Passport rules: your passport cannot have an issue date that is more than ten years old (so if your passport was issued 12 years ago and is still valid, it sadly isn’t valid for entry into the EU), and the expiry date of the passport must be more than 6 months in the future.
Visa-waiver rules: the new system is called ETIAS and it isn’t clear yet how this will work or when it will be introduced (predicted May 2023 at the time of writing), but it’ll no doubt be very similar to the US visa waiver process. Best to check nearer the time.