The advice for Vietnam has changed recently please see the details listed below from the British consular site.
The Foreign and Commonwealth Office is making changes to the notarial and documentary services offered at its Missions
What is changing?
From 13th November 2017, the British Embassy in Hanoi and Consulate-General in Ho Chi Minh City will no longer provide a legalisation service.
All documents originating from the UK requiring legalisation (such as educational certificates university degrees, teaching and EFL qualifications and other documents required by the Vietnamese authorities for work permits) must be legalised by the UK Legalisation Office and by the Vietnamese Embassy in London before they can be used in Vietnam.
Why are we making these changes?
The changes ensure we comply fully with Vietnamese law. Foreign authorities often ask that documents are legalised before they can be used for official purposes in their country. The UK Legalisation Office is the competent authority that can carry out this service for UK documents.
The changes we are making in Hanoi and Ho Chi Minh City bring our Consular services in to line with the services offered in UK Missions in other countries.
These changes are not about cost cutting. A key theme of the British Government’s consular strategy is to focus more consular resource on vulnerable British Nationals overseas. The changes will allow our staff to provide more support to our most vulnerable customers including, for example, minors, the elderly and victims of serious crime.