In order to make a visit worthwhile for people coming from abroad, YMCA England & Wales has put in place two tour options and you can see the details at this link https://www.ymca.org.uk/anniversary-tour
People can of course add days at the beginning or the end of the tours through their own arrangement.
The tours are most suited for people who may not necessarily wish to attend YMCA175 in August but who do want to be in London for the 6th June celebrations.
