Visa for transit in Britain after returning from Ireland

It is better to have a transfer visa, although there are many successful examples in Britain without a transfer visa.

As for the terms you copied, it means that if you meet these conditions, the immigration officer may consider allowing you to transfer without a visa, but depending on the actual situation, you can't completely guarantee that you can transfer without a visa.

Visa nationals refer to nationals who must hold a visa to enter the UK, and DATV nationals refer to nationals who must hold a transit visa to transfer in the UK.

DATV (direct airport transit visa)

Under the current British policy, 1 14 visa nationals and 56 DATV nationals (all DATV countries are visa countries). China is both a visa country and a DATV country, which means that you need a transit visa, even if it's just a transit, unless you make a copy here.