Depends on what time it departs - I don't think it is passed by a Leeds - King's Cross service.It takes no longer to get to the stations at which it stops than other services - it's only slower for the Leeds-Doncaster trip. Unless there are Nothern Rail only tickets for that journey, why would anyone use it to travel from Leeds to Doncaster?
It catches up the preceding LDS-SHF stopper, can't overtake it (obviously!) and avoids stops at Outwood and Sandal. Equally it needs to get to Doncaster before the 17.15 Leeds to Kings Cross. In other words it is capacity problem and doesn't bode too well for a half hourly DON-LDS service at any future date, say when Sheffield is electrified.Yes, seems to be 47/8 minutes.