The executive in charge of operations at the company behind crisis-hit Southern rail has landed the top job at the high-speed rail line used by Eurostar trains.

Her departure was announced as disgruntled Southern passengers closed in on a fundraising target in an effort to pay for a judicial review of the rail franchise.

Dyan Crowther, chief operating officer at Southern’s owner, Govia Thameslink Railway (GTR), will become chief executive at HS1, the link between London and the start of the Channel tunnel in Kent.

Crowther, who will join HS1 next year, has presided over operations at GTR during an industrial relations and reliability crisis that has infuriated passengers. Southern services have been disrupted for months amid a protracted dispute over staff shortages and the role of conductors.

The Rail Maritime and Transport (RMT) union is planning14 days of strikes from October to December.

More than 900 Southern users affected by the ongoing dispute have clubbed together to raise the cash to fund a judicial review of the franchise award to GTR. The Association of British Commuters said it has now raised £18,000 of the £25,000 needed to move ahead with the courtroom challenge.

The group’s lawyers have written to the Department for Transport asking to see documents related to the award but say their requests have not been granted.

“We have been delighted with the public response to our campaign,” the group said in a statement. “What has been extremely disappointing, however, is the Department for Transport’s failure to engage with us.

“We have asked the most straightforward of questions and have been met firstly with two weeks of silence, and now with a further delay whilst they consider whether to lift the lid on the franchise. This conduct just underlines the fact that judicial review is the only option available to us.”

Emily Yates, the group’s campaign co-ordinator, said: “It is hard to understand why they cannot be transparent about their dealings with a private company that is failing on such an unprecedented scale.”

The group is planning a protest at Victoria station in London on Thursday.