Heathrow Express dispute: Trains affected by strike
Rail services to Heathrow Airport have been hit by a 24-hour strike.
Members of the Rail, Maritime and Transport (RMT) union, including drivers, on the Heathrow Express service walked out at 12:15 GMT.
Anamended timetableis being run with trains running every 30 minutes rather than the usual 15 minutes.
The dispute, which is thought to involve up to 250 staff, follows the sacking of a driver and the suspension of a union representative.
The service connects the airport with Paddington Station.
The latest strike follows a series of industrial action by union members.
On 26 February, members staged a similar 24-hour strike, while over the weekend of 3-4 March, union members worked no extra hours.
RMT said the action was in support of sacked driver Zahid Majid and the suspension of Liaqat Ali.
Mr Majid was dismissed after an error, for which he took full responsibility, the union claimed.
In the case of Mr Ali, the RMT said he was subjected to "unfounded, spurious and discriminatory allegations" and was now facing charges over conduct and confidentiality while he was suspended.
Heathrow Express said the union was striking over an issue "which is no longer under dispute".
"The ballot centres around the suspension of one member of staff and the dismissal of another," a spokeswoman said.
"The suspended employee has already returned to work and the dismissal - which was conducted via a policy agreed with the union - has since been withdrawn from employment tribunal."