Three men were arrested when a row that started on a train spilled out onto the station platform when it arrived at Kings Langley.
The trio - aged 54, 24 and 22 - were arrested on suspicion of affray and a 19 year old man was cautioned for being drunk and disorderly.
It happened on board a Watford to Northampton train following a Stone Roses concert at London’s Finsbury Park on Sunday, June 9.
Anyone who saw the incident is asked to contact British Transport Police on 0800 40 50 40 or text 61016, quoting reference B6/LNA of 20/06/2013.
Information can also be passed on anonymously via Crimestoppers on 0800 555 111.