I am tackling it slowly.
This cupboard was basically just piled with stuff when we moved in here. Stuff that didn't have a home but needed putting out of the way. This included three bin bags of non-essential washing (no washing machine at the old house), lots of boxes and assorted other junk.
Last week I filled a black sack full of assorted things from under there.
Today I filled another one.
I can only do one black bag a week because with all the other stuff I am throwing from the garage etc that is all that will fit.
Despite the fact that I have only thrown out two bagfuls and taken another bagful of clothes out to sort and wash (as they're mine and nice), the cupboard is looking much less scary.
I daydream of the day that its empty and I can store the hoover in there.