This is most likely couch grass, keep on digging.

If they are white in colour then very likely couch, if more of a beigey/brown then they could be Bishop Weed aka Ground Elder. This latter is a broad leafed herbaceous plant and I prefer to get rid of it by rubbing Round-Up onto the new leaves.
With either, when you are digging try not to break any bits off as they will grow again.

Thank-you Bob is that the only treatment?

Yes - if there are any plants with it growing through them, it's best to dig them out carefully, get the grass out, and dig the area to clean out every scrap of root. Then you can replant your plants - and water them well!

Couch grass is a menace. I sympathise! :-((

Thank-you bulbaholic I think it's more likely to be couch grass as there are no leaves.do you think roundup will kill it?

I've found doing it the quick way with Roundup, you will not kill all of it. Leaving some will mean you will have to start again next year.

I wouldn't particulary fancy brushing round-up on all the blades of couch grass, Tulsa, I think that you have to do this the hard way.

aw no there's masses of roots we'll never get rid of it by digging alone.:o((

Tulsa, are these roots amongst flowering plants or are they in open ground, such as a new allotment plot? If the latter with no important plants nearby then spraying with a herbicide, such as round-up might be your solution. Otherwise I am afraid that you have a lot of digging ahead of you.
Do you have any younger relatives that could come and help - hey, it will soon be Bob-A-Job week won't it!

Bulbaholic I don't think the scouts have bob a job week now do they ?,more like tenner a task LOL.lucky for us there are no plants around that plot, we had our grandaughter pulling the roots out yesterday to earn her pocket money,poor kid but she really enjoyed it.

Ground Elder is very difficult to get rid of as each time it breaks the root will continue to sprout. In between plants get a plastic bottle cut off the top and bottom put it over the Ground Elder and spray with round-up. The bottle protects the leaves of your plants.

Thank you all for the advice,I think we have a lot of digging in front of us.