Getting to known which dates the Vietnam Embassy London does not work seems to be very important for you if you have work to deal with the embassy.

Following are the public holidays of Vietnam Embassy in UK this year, 2016:

Date Public holidays
Friday 25 March 2016 Good Friday
Monday 28 March 2016 Easter Monday
From Saturday 16 April to Monday 18 April 2016 Vietnam Commemoration Day for Hung Kings
From Saturday 30 April to Tuesday 3 May 2016 Unification Day and International Labour Day,
Early May Bank Holiday
Monday 30 May 2016 Spring Bank Holiday
Monday 29 August 2016 Summer Bank Holiday
From Friday 2 September to Sunday 4 September 2016 Vietnam’s National Day
Sunday 25 December 2016 Christmas Day
Monday 26 December 2016 Boxing Day
Tuesday 27 December 2016 Christmas Day (substitute day)

So, if you want to contact the Vietnamese Embassy in London, UK to deal your work, including seeking for information about Vietnam Visa, please take a look here to make sure you do not waste your time for nothing.