In the paper A Note on Triple Transitive Graphs, Cameron gives an almost-complete determination of triple transitive graphs with girth greater than $3$. In the remark at the end he says:
"If, as seems likely, the only graph occurring under (iv) is the Higman-Sims graph (with $\mu = 1$), then..."
Has this been resolved by now? Are there other triple transitive graphs of diameter $2$ that appear in (iv) of the classification?