Flying London to Beijing via Hong Kong

Hi I am considering an itinerary where I fly on Cathay Pacific to BJ from London. There is no direct Cathay Pacific flight, so I must transit in Hong Kong before going to Beijing.

But the second part of my trip is Beijing to Hong Kong, and after 1 week in Hong Kong I will then return to London.

Although the first stop in Hong Kong is part of London to Beijing route, will I qualify for the 72 hour free transit since I will be arriving in Beijing on the leg from HK, and my next leg is to HK?