While I'm on this subject. The UK has very stringent border and immigration controls. A case in point.
A British citizen married an Argentinian Doctor and they had one child in Argentina. She was a housewife with no personal income of her own. They decided to relocate to the UK. Her Doctor husband had a Spouse Visa that expires after 3 months as do all visas.
When he applied for residency, it was refused and he was sent back to Argentina to reapply for a visa. You cannot apply for a visa inside the UK.
The reason for the refusal is that the British spouse must sponsor the third country spouse. To do this she had to have an income of around R27k pm or savings of R1.8M but as she was a housewife she had none. It does not matter that her husband is a high earning Doctor.
British citizens bringing in a foreign spouse now have to use the EU Treaty laws. To do this, they have to live and work in an Shengen member state for at least 3 months and get residency in that state. Then enter the UK using Treaty Rights as it overrides UK's internal laws.
This can be done via Ireland as many do due to the language. South Africans can enter Ireland without a visa and can apply for residency if the spouse is an EU member citizen.