X-rated Bob wrote
I don't know about the Magalies Express (well... it has the E... word in the name). Scheduled time is about 1:50 to Magaliesburg and 2:05 on the return leg. The return leg takes longer because there's an uphill run into Krugersdorp. I don't know what sort of speed that equates to or if, as in the UK, the trains are forced to travel slowly because of compliance with safety regulations.
I shall report back!
OK... firstly this by no mean the only historic rail service in SA. Those of you around Pretoria might make some enquiries about "Friends Of The Rail". I know there's something going on in KZN too. One of the staff on the Magalies Express told me that there's several such organisations but couldn't give me details there and then.
Here's the engine that pulled the train we rode on Saturday

15F class. Number 3406. 4-8-2. Built in Glasgow in 1945. Pulled the royal train in 1947. Retired in 1988.
This is the train steaming up the hill out of Magaliesburg on the return leg
The rolling stock isn't in great condition, but I think it's authentic for the period and you'll be safe and won't catch anything nasty. There's a bar coach and a refreshments coach - prices are very reasonable.
The big drol in die drinkwater is that they have to use SAR lines. A lot of the historic railways in the UK own their own lines because of government shut downs in the 60s and 70s that shut down many branch lines. Government didn't want them, so they got bought up by trust funds set up by steam enthusiasts (the Severn Valley Railway that I rode on last year owns 16 miles of track and the stations and all the ground along the line). That hasn't happened in SA and the actual rails and routes are still under the control of SAR.
This means, for example, that the Magalies Express has to yield to all commercial traffic on it's route and this can mean delays. On Saturday we left Jo'burg about 30 minutes late and got back something like 3 hours late.
It is a fun day out. The whole business of going somewhere but not having to drive or deal with people who make a last minute dash through the robot as it goes green for you etc etc was something I enjoyed. Because you don't have to watch where you're going you can look at things in a different, more relaxed way. We had a compartment for 6 (a little more expensive, but you have a piece of turf that's yours) and so we could sit and have good conversation and watch life and the highveld go by. People who knew about steam engines were getting all lekker listening to the noises that it made.
But don't look at the time tables and plan according to that. Reef Steamers do make an effort, but ultimately it's not their lines and, as I said, they get low priority if two trains want the same piece of track. We were three hours late getting back despite having a perfectly healthy train.
Oh... speed. The lines are all speed limited and there are camera traps ? to catch any drivers who are being windgat. Reef Steamers got bust a couple of weeks back doing 78 on a 70 km/h section. They can easily exceed the current speed limits on the tracks but try not to. We got up to about 80 ks on one section, but couldn't do that speed for the entire route because of the aforementioned limits.