This is the white filter pad located above the motor (under the clear bin). Yours may not look white, may be a grey/black colour from the years of motor carbon dust. These filters are not designed to be washed, which is why they are best to be replaced. If your filter is a thick plastic filter then you will need the HEPA filter that can be found below£2.45
Dyson DC07 HEPA Filter Kit
Dyson no longer make these filters, however we can offer this great after-market alternative. This will fit all versions of the DC07 models. You may have a white post motor filter instead. This HEPA filter can replace that and is more suited for pet owners or people with dust allergies.
If you would rather buy the filters on their own you can find them below. This kit contains:
1 x DC07 Pre Filter
1 x DC07 Post HEPA Filter