Am I able to catch the high speed train from HK to Beijing to see the Great Wall of china

Hi there, I'm a from the UK with a UK passport, I am currently travelling Hong Kong with my girlfriend who is also a UK citizen, we were wondering if we are eligible to get a visa pass and if so which one, we wanted to see the Great Wall of china on our HK visit, but we will be going back into HK on the high speed train, also we are leaving HK on Monday 27th November 2017 to go to Japan. Many thanks