On Wednesday, Transport for London (TfL) announced it would invest £15m on building more toilets across the network and improving existing facilities.

For Billie Nicholls, who has ulcerative colitis, the news means she will be able to travel without “worry and stress”.

The 28-year-old from south-west London said toilet access for someone with a gut or bladder condition was “really important”.

She was diagnosed with the chronic inflammatory bowel disease in 2017 and has been living with a stoma bag for seven years.

TfL said it would increase the number of available toilets from the current number of 185, external so that customers were “always within 20 minutes of a toilet without having to change train”.

It added that construction work was expected to start within the next year.