On my goodness - we are back to the Covid diaries. Here we go again. No sooner than I had achieved my best new immunity from my latest Covid-19 vaccine jab than Omicron appeared.

Omicron is a novel variant of SARS-CoV-2 first reported in southern Africa. There, it has out-competed the earlier and previously dominant Delta variant, and its doubling time is surprisingly short. It is wildly infectious and a very efficient immune-escape variant.

Three weeks ago, I had my third Covid-19 vaccine. This time, I had the Pfizer/BioNTech mRNA vaccine, having had the AstraZeneca vaccine for the first two (a six-month gap between second and third). Early data from UK health surveillance indicate that this combination offers protection against Omicron that is about as good as possible at present.

While it is not yet dominant here in the UK, Omicron infections are doubling quickly. Very sadly, as I write this, the first death "with" (i.e. not necessarily "from") Omicron has just been reported.

Over the last couple of months, I have been venturing back to London for some shutter therapy on the streets. I have been enjoying drifting around London, camera in hand, for the last couple of months for the first time since before the first lockdown in March of last year. But now, Omicron puts that back into question.

The rainbow across the Thames at the start of this entry is from one such recent trip.

My daughter is just starting a new job. She needed a new headshot for her employer's website, and, of course, I was delighted to do that for her. She suggested we take a walk to the Thames opposite Canary Wharf: she liked the idea of something characteristic of London in the background of her portrait. We took a fascinating walk from where she lives in South London across to and along Deptford Creek, up to the Thames path on the south side of the river. (Incidentally, our first stop was at Middleton's cafe on Loampit Hill - a full English breakfast for lunch - highly recommended!)

The weather was very pleasant as we walked up; but once we got to the Thames, we could see a rainstorm approaching from upriver. I only finished the portraits she wanted a few minutes before the rain arrived. Its approach was marked by an amazing rainbow that started over Canary Wharf; shortly after, it became a gorgeous full bow stretching from there to Greenwich. From where we were standing by Deptford Creek, the rainbow seemed to end at the entrance to the Greenwich foot tunnel.

Moments after getting the pictures shown here, the rain arrived and we both ran for cover in the entrance to the Greenwich foot tunnel - but no pot of gold was to be found in there :(

Once the rain eased up, we made our way over to another enjoyable cafe in Greenwich Church St for some much-needed tea and cakes as we dried off.

I can't remember the last time I saw a rainbow starting on one side of the Thames and ending on another - worth getting wet for!

That was a day when I felt fine about being out and about in Covid time. My third vaccination should have kicked in, and I felt well-protected. Omicron has changed that.

We are still in the land of known-unknowns with Omicron. How infectious it will turn out to be over the next few months in UK winter conditions remains to be seen, as are rates of hospitalisations/fatalities etc. Of more immediate concern is how infectious it will be for someone like myself, treble-jabbed, in an indoor environment. Outside, I feel like there is little risk because infectious aerosols from people's breath disperse rapidly. But inside? At present, Covid case rates are (surprisingly) worse here in parts of east Kent than in central London. In that sense, I might as well carry on where I left off and enjoy photographing in London; but Omicron might simply put me off altogether.