I migrated to Australia in 1974 with my 5 month daughter on my British passport. This passport expired in 1984, was never renewed, and has been lost for many years. For work reasons my daughter needs to provide the number of my passport. She has, in fact, lost her job even though she has her own British passport. Apparently someone in the human resource department where she was employed decided she is not eligible to work in Australia. I have searched everywhere I can think of but to no avail. Does anyone know where I might find this number???
This has come up on Travel.SE before, and so I quote the relevant parts that apply:
If you had pages of your passport certified by a solicitor or notary, they would also have taken a photocopy of the portrait page. Law firms have a varying retention framework unlike companies, and many like to preserve their archives for a long time.
If these fail, and as a last resort, you can file a Subject Access Request with the Home Office. There is a fee for this and you must clear hurdles imposed by the Data Protection Act. A Subject Access Request obliges the Home Office to give you their records about you along with what they know about you... if they want to. The SAR must be in writing.