The message
from "Brian" contains these words:

Seaweed is one of the finest additions available. There is no need to wash
it or even to use as compost. Simply dig it directly into the ground.

I agree. If you're digging a bed for some reason, it's an excellent
idea to incorporate the largest possible volume of seaweed. But it's
equally effective spread on top as a mulch; it decomposes into the soil
so fast that a 6" layer put on now, will have disappeared by the end of
summer.

If you're planting potatoes, do both; lay it in the trenches under the
potatoes, replace the soil, and cover the whole bed with a thick mulch.
In one fell swoop you're fertilising, protecting young shoots against
late frost, preventing weed germination, and discouraging slugs and
diseases.

( It's also an excellent decomposition-booster in the compost heap).

Janet.