Further Clarification on second entry into Beijing within a week.

Again thank you in advance. We are travelling the following itinerary and the first leg was kindly clarified but would be grateful if anyone can help and clarify if I would have any issues returning back into Beijing after a four night stay in HK before flying back to LHR. Itinary as below:
LHR to Beijing for 2 nights
Beijing to HK for 4 nights
HK to Beijing overnight stay 8 hours in Airport Hotel.
Beijing to LHR.
On arrival back into Beijing from HK can anyone clarify if i need to do anything on arrival and what is the procedure on entry.
Is a visa required at all for this visit.
Many thanks