Bank Voles !

I hold the national collection (involuntarilly)

Your lovely raised beds are perfect BV hotels (much better than a common field!)

Gravel won't help. They will either move it or simply climb to the surface of the bed and burrow down into the beautifuly comfy home you have created for them. If you concrete the boards in it may stop them 'scouting' the edges of the bed and systematically emptying them of soil, if the sub soil is compacted enough. I've heard that if you cover your RBs with stapled plastic sheet, it will prevent them climbing but I'm sceptical

Have you seen them ? They're so cute... sorry that's not helping is it !

IMHO they don't readily take from traps. Bait boxes may work early in the season, but as soon as there are alternative food sources they ignore them. Ever seen a 'ickle bank vole in the throws of a warfarin stupor... It's so horrid... not to mention the possible effects to animals higher up the food chain.

Sorry.. that really isn't helping !

Physical barriers will make your Vole Hotel less hospitable. Notice how they tunnel around established plants. Start seed off in a vole proof seed bed or in large pots (about six inches tall, with no nearby launch pads early in the season) and transplant when stronger.

Remeber that they live in grassland and generally won't eat your plants. They've moved in because of your lovely soil... not for food (tho they love Aquilegias in spring!)

Tamp down and water their tunnels to stop plants capsizing. That brings me to another point mentioned by our council pest bloke... remove all sources of drinking water for them in spring.

It will get better as your beds settle but, your proximity to a field suggest that you may have to make friends at some point.

Good luck