Lost plant label - can you identify?

I lost the plant label on a tray of little seedlings. They took several weeks to germinate, and are very slow progressing. They are now approximately 7cm high, very delicate. The stems are reddish and very thin, however there is a nice rootball an all of them. I can’t think what they are, I went through all my seed packs, but nothing looks right. Saying that, I order from the RHS seed scheme every year, and it might be one of them. Does anyone has an idea?

I did use the plant finder app, which came up with Rubus strigosus, but this does not seem likely - no seed packet by this name and doesn’t ring a bell. It might be an interloping weed, but it was a neatly sown 9 seedling tray all with the same plant.