Anyone know?

Definitely not nerines Lemongrove I ve got a garden full of them they are quite different bulbs to these tubers and I ve also got Montbrezia and it’s not them either

Dahlia is my answer too.

They don’t look like agapanthus or dahlia to me. They look more like the cultivated bluebells I have to dig out every year. That would explain why there are so many of them in the pot because they’re very prolific reproducers.

Difficult to be sure though without knowing more about the size of bulb and leaf.

They do look like dahlia tubers but 'tall thin green leaves' doesn't sound like dahlias, more like agapanthus. If you type agapanthas bulbs or dahlia tubers into google and then select images you will see some pics which may help you decide.

Not a dahlia leaf more like the agapanthus leaf but the tubers are not big about an inch to inch and a half I ll try and get a better photo tomorrow too dark at the moment
Yes it ll be a nice surprise if they do flower this year

With not much to do, laid up with the lurgy, I’ve thought about this and have changed my mind to Day Lily tubers. That would also go with the long leaves.
They definitely need to be in full sun.