The great news is that after I dealt with this one, no more came up in the last few months!

Looks like it might have been a stray seed that got into my lawn from elsewhere.

I recommend the PistureThis app - but it's rather better at identifying tree types and with the millions of flora types it cannot id everything - still useful though - I found a tiny oak and an ash tree growing in my garden!

Thanks for the recommendation of PictureThis!

Tried it and it immediately got the right weed : purple deadnettle

Guessing it must be in gardens around me in the Nightingale Triangle, as it isn't a weed that was present in my lawn before.

Looks like some Roundup or Resolva spray will get rid of it easily.

I downloaded a rather good app the other day called PictureThis which tells you which plant is which when you take a photo of it.
There is a free trial but I've just let mine run as I'm useless with plants and it's been fun for the kids.

Saw these growing at the edge of my grass lawn. Haven't seen these before, and a quick Google search doesn't yield anything familiar in terms of weeds.

Anyone know what they are?