Have a colleague whose headed to the UK on a single entry work visa in June. He's flying MAA - CMB - LHR for the onward sector. On completion of his work in the UK, he intends to travel from there to YYZ for a week.

Can the same 'Visitor in transit visa' facility be utilized for his return segment; where in he flies YYZ - LHR on a separate ticket & then connects on a UL ticket for the LHR - CMB - MAA. leg ?