I've just landed into the UK from my flight and even though I was in the UK 5-6 days ago, I didn't need to fill out a digital registration for Germany form as I was staying less than 24 hours in Germany. Also, people from High Risk Areas don't need any test as long as they're fully jabbed - this is what the QR agents told me at check in.

The agents in Dammam were really good and checked my bag all the way through to LHR, no issues at all. This was extremely useful in this instance because when I landed, the line at FRA for immigration at T1 was nothing short of a nightmare. Glad I didn't have to go through that and I was there as a transit pax only.