The week long postal strike that began on August 21 is set to hit London for three days starting from Thursday August 27.
The latest postal strike organised by the Communication Workers Union (CWU) is one of the largest in the recent past with up to 20,000 postal workers participating in the walkout.
Thursday, August 27 will witness industrial action across many parts of the country including Birmingham, Coventry, East Midlands, Bristol, Cambridge and London.
In London alone around 700 staff are set to walkout on Thursday and Bristol will see 800 workers taking part in the postal strike.
The postal strike will hit London harder on Friday and Saturday with around 3,500 workers walking out at the London Division Mail centres. Edinburgh will also see 900 mail centre and distribution drivers participate in the strike on Friday.
Delivery offices in London will be hit hard with 7,500 workers joining the industrial action on Saturday.
Royal Mail has advised customers that deliveries in parts of Cambridge will be affected by the strike on Thursday.
Friday will see mail collections affected in London for all post codes except W5, W7 and W13 and the deliveries in London will take place as usual except in the EC areas where deliveries will be limited.
On Saturday, 29 August, collections will take place as usual while deliveries will be limited in all post codes of London except EC.
Tuesday will see deliveries and collections affected in EC area of London and parts of Cambridge and Thetford.