The former Leeds Rhinos star arrived at the University of York's sports centre on Monday (Sep 28), where Princess Anne met his running team and joked about joining them on horseback.
Sir Kevin completed four laps of the university's athletics track alongside supporters before the Princess Royal struck a drum seven times to send him on his way.
The visit formed part of 7 in 7: The Grand Finale, which will see Sir Kevin complete seven ultra marathons in seven days.
Inspired by his former teammate Rob Burrow, who died in 2024 after living with motor neurone disease, Sir Kevin and his team have raised more than £11 million for the MND community since 2020.
His final challenge will finish at Old Trafford ahead of the Super League Grand Final.
9. Sir Kevin Sinfield on day two of the 7 in 7: The Grand Finale 2026 Challenge - Shiptonthorpe to Bishopthorpe.
Sir Kevin Sinfield 7 in 7 | Mike Egerton/PA Wire
10. The Princess Royal at the University of York Athletics Track, on day two of Sir Kevin Sinfield’s 7 in 7: The Grand Finale 2026 Challenge (Dominic Lipinski/PA)
Sir Kevin Sinfield 7 in 7