On an open, straight road, a giant tortoise can actually hit quite reasonable speed.
(Not my image, so I didn't actually measure this buddy's speed, sorry. I don't know where this was actually taken or what tortoise species this is. This may LOOK like a left hand drive country, but do the tortoises know the traffic laws? ...that's another matter, you know.)
Having worked with several large tortoise species, this is true. They can be much quicker than you expect, especially when they notice you have their favorite food.
It looks like either a Galapagos or Aldabra but I can’t tell for certain.
It’s similar to a pretty normal human walking pace, more a “walking up to a restaurant to meet your friends inside” speed than “slowly strolling through a museum looking at art.” If that makes sense? Fast enough I’d have to step quickly to get away when I’d see the one tortoise who liked to use my pants as her napkin heading toward me with bits of food stuck to her face.