All Chiltern Railways lines between London Marylebone and Aylesbury are blocked this evening as the emergency services deal with an "incident". 

Train services running to and from these stations may be cancelled, delayed by up to 60 minutes or suspended between London Marylebone and Aylesbury.

All stations between Harrow-On-The-Hill and Aylesbury will not be served.

The incident is believed to have happened in the Harrow-On-The-Hill area. 

Disruption is expected until around 9pm.