The two materials don't really go together in many people's eyes.
Well done tarmac can look good, but its associated with being a cheap an cheerful solution, even though it costs money to do it well.
Gravel, OTOH seems to be associated with wealth and prestige, although it is a difficult surface to walk and doesn't comply with Part M Access for the Disabled.
Whatever you do tarmas needs an edge or it will crumble and erode, so perhaps a pavoir edge might be useful or a concrete kerb.
ONQ.
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All advice on AAM is remote from the situation and cannot be relied upon as a defence or support - in and of itself - should legal action be taken.
Competent legal and building professionals should be asked to advise in Real Life with rights to inspect and issue reports on the matters at hand.