How to restore leather on an Erik Worts safari chair?  

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You don't want to restore the piece to it's original state, the quality vintage look is the thing that is desirable. Like the threadbare oriental rugs that have been in the ol' family castle for generations, you don't re-weave them; you just keep them clean and enjoy the intrinsic high-quality. The primary care for leather is to not spill on it and basically do nothing-- but just like your own skin, seasonal changes in temperature and humidity etc. can cause the leather to dry out. If the chair is dry, then condition it, just like you might apply lotion to your hands. Dr. Tork Leather Master is one example of a product you might use for this.

Thank you - so you disagree then with the idea of using neatsfoot oil? I have no desire to get it looking new - perhaps

Neatsfoot oil is okay for your baseball glove, but I'd keep it away from the fine furniture.