The first was on Thursday, May 10 at St James's Church, Clerkenwell, London EC1R 0AP but there are lots more events around the country later in the year.
We want to give glory to God for all he has done through SIM since we were founded 125 years ago but also look forward to serving the gospel needs of a world in which more than two billion people have never heard of Jesus.
To book your place, or if you want further information, please click on the 'Book Now' button at the top of this story.
The exact venues are still to be decided but the regional events are:
Scotland, September 26
Manchester, October 6
N Ireland, November 2
Birmingham, November 20
Bristol, November 21
Southampton, November 22
We will confirm exact venues nearer the time, but do put the date/dates in your diary.
To commemorate the anniversary, SIM International has published 'By Prayer to the Nations', a history of SIM written by Gary Corwin (cover illustration right).
The book runs to more than 400 pages and features some wonderful stories from SIM's pioneering missionaries, as well as lots of illustrations.
It's available for just £15, plus £5 postage and packing. Please email communications manager Tim Allan (email@example.com) to reserve your copy.
Click here to read more of SIM's current work and how it is very much a continuation of the vision of our founding fathers, who first arrived in Lagos in 1893.