You got me curious, flairball, so I checked the Standing Council of Scottish Chiefs' website. It has Malcolm K. Mackintosh of Gwelo, Zimbabwe as the Chief of Clan Chattan.
http://www.clanchiefs.org/chiefs.html
It could be that their site is out of date, as they still have Lachlan as the Chief of Clan Mackintosh in their clan history, but it does tie in with what I had read previously. But I'm still puzzled :confused: . Does your convener know how the two chiefships were reunited?