Where, under this Part of these Regulations a date of development must be determined for the purpose of a claim for benefit in respect of pneumoconiosis or byssinosis suffered by a claimant who is or has been entitled in respect of the same disease to any compensation under the Workmen's Compensation Acts, the disease in respect of which the claim is made shall be treated for the purpose of these Regulations as not having developed on or after 1 May 1967.