YAY! It is crown vetch I don't know why I could not remember that myself! Thank you very much... my leopards have been having a go at some and I think I remembered it being toxic to horses but could NOT recall the name to check it's safety for the curious leopards. Really appreciate you : )
Some species are toxic, but I think its the seeds more than the plant. And it is planted in some pastures for horses and cows, so I think it would be ok for tortoises.