The under-the-skin injection has recently been approved by medicines regulators in Great Britain and Europe.

MS affects more than 150,000 people in the UK, with some 135 people diagnosed each week.

The lifelong condition is caused by a person’s immune system mistakenly attacking the protective covering that surrounds nerves in the brain and spinal cord.

Messages travelling along the nerves may become slowed or disrupted.

This can lead to a range of problems including difficulties with eyesight, movement, sensation and balance, and it can cause serious disability.

Ocrelizumab (also known as ocrevus) which is given twice a year, targets a specific part of the immune system, helping to lessen the attack.

It can be used for two forms of the disease – active relapsing MS and early primary progressive MS.

In the most common, relapsing remitting type of MS, the disease waxes and wanes with episodes or flares where MS is active.

In other cases it be progressive, with symptoms gradually worsening.