Hasn’t that been around a couple of weeks now? All persons entering UK should fill it in. Just fill it in on smart phone before entry, and show phone to Border Force if requested.
They asked to see mine in Pompey, but not when using the Tunnel.
Maybe it will become redundant in the next few weeks, as many neighbouring countries have lower C19 rates than the UK.? Reciprocal access “air bridge” or some such?