The union plans to take harder measures to fight their campaign as around 120 members are now staging protests at both the National Museum of Scotland and the National War Museum which is planned to last until Sunday.

3392914538 Strikers at the National Museum, Edinburgh
Image via Edinburgh Evening News/Scotsman

The strike will hit Edinburgh's culture industry hard as the strike runs simultaneously with the Edinburgh Festival. The strike will in no doubt hinder visitors to the museums, although the sites will remain open.

The union issued this statement:

"A two tier workforce now exists in the museum, with those employed before January 2011 receiving the allowance which can amount to between £2,000 and £3,000 a year for staff who work weekend shifts."

"These are low paid workers and this allowance makes a big difference to the lives of those who receive it."