New residence permits for UK nationals

Posted by: @vianina

the worst that can happen is a two-hour detention while you arrange for someone to bring your ID. 

Thanks, that's a very informative read. Having just looked at Article 250 of the Criminal Procedure Code it appears to have increased the maximum permitted detention time from 2 hours to 6 hours.

Whilst the media report makes no mention of it, Article 250 CPC says ID can be requested;
Os órgãos de polícia criminal podem proceder à identificação de qualquer pessoa encontrada em lugar público, aberto ao público ou sujeito a vigilância policial, sempre que sobre ela recaiam fundadas suspeitas da prática de crimes, da pendência de processo de extradição ou de expulsão, de que tenha penetrado ou permaneça irregularmente no território nacional ou de haver contra si mandado de detenção.

Obviously the "entered or remains in national territory" leaves all of us who are immigrants liable to being asked to produce ID whenever we are in public.

some info about our wonderful bureaucrats

Almost 35,000 Britons in limbo as Portugal fails to issue post-Brexit ID cards | Brexit | The Guardian

Posted by: @vianina

but my assessment is still that the risk of harm from carrying it (loss of passport, expense of a replacement, time without ID, possible missed trips) is greater than the risk of not carrying it (up to 6 hours in custody divided by the slim probability of being asked by the police to produce it).

I only seek to inform forum members when I'm aware of a consequence they might not have knowledge of, having done so members have free will and make their own decisions.

I was concerned about passport loss hence why my wife and I carried certified copies of our passports. The time and cost of obtaining them was less than the consequences of being unable to produce our passports if required.

Posted by: @vianina

they'd need well-founded suspicions (fundadas suspeitas) of the person having entered or remaining unlawfully in national territory

Who decides what a well-founded suspicion is? It's a subjective decision by the person making it. Ultimately it would be up to a court to decide if it was well-founded, and that will be 5-10 years in the future after you've complained about being detained and fined.
I've better things to do with my life than spend up to 6 hours locked up and then years afterwards arguing that I shouldn't have been.

How does one "certify" a copy of one's passport please?

Posted by: @vianina

(a) the likelihood of that being asked to produce ID is pretty low

Agreed, but it does happen.
The likelihood of my home falling down due to an earthquake is also low, but I still take out insurance for that eventuality.

Posted by: @vianina

(b) carrying ID is not an obligation, contrary to popular belief, and failure to do so won't bring you either a fine (unless you were driving) or imprisonment.

Those who have been fined for not carrying ID would disagree with you.