Why do MPs not need to wear face masks in the House of Commons?

manchestereveningnews.co.uk:

The use of face coverings have been made mandatory in a number of places in England since the coronavirus outbreak.The first ruling was for passengers on public transport in summer before it was expanded to supermarkets and other enclosed public spaces.Primarily, the rule is in force where it is difficult to maintain the two metre social distancing.As the country was encouraged to head back to work, businesses were told they had to be 'Covid-19 secure' in following the latest government guidance.In some cases, this meant that employees would have to wear face masks in the workplace too.But many members of the public have claimed MPs in the House of Commons have not been adhering to the Covid rules by not wearing masks.So why is it that MPs.