Comment by fwip
If you google it with the words next to it, 'Home Office TCN' (no quotes necessary), the proper definition comes right up.
It's written for a UK technical audience, who is likely familiar with these terms. An American article doesn't bother to define "FBI" or "USDA," and an article about breaking Python news doesn't expand "PEP" or "RFC."
Try any of those example acronyms (which are far more common in search indices IMO "in my opinion" :) and they will be immediately disambiguated by Google's top results. Type "TCN" and "Technical Capability Notice" doesn't show up after 4 pages. I needed to use an LLM and provide a paragraph of context for it to learn about it.