3N perjury is technical - Perjury Act 1906
the hurdle is high - there has to be an independent witness to the act complained of
IN R v Adomako a medical manslaughter case, a nurse said Dr A was drinking milk in the ward kitchen when he had said he was with a patient.
There could be no prosecution for perjury because there was no other witness to back up the statement.
You will have noticed people lie every day but there are very few prosecutions for perjury