"suspect did not sufficiently invoke the right to remain silent when he stubbornly refused to talk:"
http://www.slate.com/articles/news_and_politics/jurisprudenc...
In this case, the suspect had spoken to the police, and during this didn't respond to a certain question / responded to the question with silence. If I recall correctly, the court reasoned that by first speaking, he gave up his right to remain silent. Moreover, he responded by silence rather that actively asserting his right to remain silent.
Not to say I agree with the ruling, especially because he was never mirandized. However, it is not clear cut that simply remaining silent isn't enough to assert your right against self-incrimination.
> You do not have to say anything. But it may harm your defence if you do not mention when questioned something which you later rely on in court. Anything you do say may be given in evidence.
the wikipedia article goes into details: https://en.wikipedia.org/wiki/Right_to_silence_in_England_an...
https://www.gov.uk/arrested-your-rights
I imagine there is a sizable amount of injustice in the UK due to not having a 4th amendment like rights.
From your quote we see that this is not the case in the UK. Something you say can later be used in your defense, so clearly if you choose to say nothing -- you have less that could be used in your defense.
> I imagine there is a sizable amount of injustice in the UK due to not having a 4th amendment like rights.
Compared to the US?
This has lead to a lot of unsound convictions of people who were intoxicated at the time of arrest; They tell some abridged version of their story to police, leaving half the important details out, leaving them with half a case to take to court. In Scotland they have started Requiring solicitors to be present at interviews of suspects (of some crimes) because of this, making statements inadmissible unless a solicitor was present.