The Edinburgh Mathematical Society ran Colloquia in Edinburgh in 1913 and 1914. After a gap caused by Word War I the meetings resumed in St Andrews in 1926 and seventeen summer meetings were held in St Andrews.
A number of famous mathematicians have attended these colloquia and you can see pictures of them at the links below. The photographs also give a good idea of the British and more particularly Scottish mathematical scene over this period. Since it was customary for many mathematicians to bring their families to enjoy the delights of St Andrews away from the lecture rooms, these pictures show wives and children also.
Unfortunately, no photograph of the 1914 meeting is available.
The 1913 meeting
The 1955 meeting
The 1980 meeting