Mismatch between TfL journey planner and National Rail Enquiries

[arb]

I'm looking at times from Kew Bridge to Waterloo for a journey a week on Saturday (25th March) between at approximately 4-6pm.

According to National Rail Enquiries, trains are half-hourly at xx16 and xx46.

According to the TfL journey planner, trains are half-hourly at xx26 and xx56.

I used RealTimeTrains as a tie-breaker, and am therefore assuming that xx16 and xx46 are the correct times (and also, using these times means I'll only have to stand around for 10 minutes instead of 20 if I'm wrong )

But does anybody know why TfL and NRE (both of which I'd consider as "official") would be giving different results? Is this a one-off glitch or does it happen often? Is there a reliable way to know which is correct if I spot them differing again in the future (which I guess means a way of finding out which one has been updated with timetable changes most recently)?

 

[87015]

Don't use TfL for national rail services, the TOCs don't send their data directly to it so it's often behind the live data. Long-standing farce.

 

[arb]

That's a shame. I've always found the TfL planner gave much more realistic connection times for mixed train/tube journeys than any rail booking site. Guess I'll have to mix-and-match the planning of such journeys in the future.