Probably a weed since it was in the topsoil but can you post a photo to be on the safe side?

without a picture difficult to say but from the description bronze fennel.
if you dont want the plant dig them out. your garden grow what you like as long as its legal!

welcome to Goy too.

Thank you both. Here's a couple of photos.

Not fennel then. But it doesn't look like any weed I can think of. I wonder if it might be a Lysimachia - there is a tallish red leaved one just that colour that has yellow flowers and it spreads readily by runners. It can be controlled if you want it by removing all the parts you don't want when they come up around the parent plant in Spring. If that's it then its something for the herbaceous border. (And you'd only need one!)But I don't think it has hairy stems. A puzzle.

Thank you Steragram. I think you could be right. I just pulled one clump up, and it was difficult. The runner root ran along to another plant, so I think I'll have to remove all the ones that are in the way of the shrubs and perennials I've planted this year. I don't know where the parent plant is - perhaps in my neighbour's garden. All mine are the same size, but growing apace.

It does look like Lysimachia 'firecracker'. so a weed if you don't want it an nice plant if you like it.

Yes, it's lysimachia 'Firecracker.' A good plant, but a spreader

if this was brought in with the topsoil I'd complain to the company you bought it from. This could have been japanese knotweed and that would have been a disaster. these plants havent come from seed but bits of root in the topsoil.

Good point. The company who built the large flower bed provided the topsoil. I'll try to establish where it came from. Thanks to all for the information.