Thank you all to the good advice on this train. I have reservations and and not worried now about the transfer in Rotterdam.
Starting RS tour in Haarlem Netherlands in May . I'll have 2 days in London then I want to take the train from London to Leiden Netherlands. Then next day Leiden to Haarlem Netherlands. Seems like a lot of transfers and travel time, any suggestions, maybe skip Leiden and just go strait to Amsterdam or Haarlem.