Can you help us identify this weed?

Will Barnard has yellow and red weeds that are his major issues in his newly established Typha crop. We have identified the red culprit as Willowherb. We have a range of suggestions for the yellow one... Picture above.
I think it is probably lesser spearwort; the suggestion from the team in the Broads is Buttonweed (Cotula coronopifolia).. Any agronomist or botanist thoughts welcome.
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