My partner is planning to travel on Thursday morning from Euston to Penrith for work purposes and then return sometime Friday afternoon to Watford Junction. Outward not a problem to book 0910 (First train an off peak return is valid) However it's difficult to say what time she will get to Penrith she will try to get the 1703 departure but may be in time for the 1621 or may late and have to get the 1804. If she has a seat reservation on the 1703 is it likely to be a problem on the 1621 or the 1804 without a reservation?