The Chatham Main & Medway Valley Lines add-on, which was released last year, is on free trial until Monday, 6pm (UTC). You won't be able to play it for free after that date, but it has an interesting discount: for the same price as the Chatham Main Line alone, you will also get the Medway Valley Line! Indeed, DTG offers us here a combination of two routes and since the Medway Valley Line is not available separately, I will focus on this one - especially because it is less well known to the public than the Chatham Main Line (CML).
The Medway Valley Line, as its name suggests, follows the Medway River along a north-south axis in Kent. In-game, the route starts from Strood (station connected to the CML) and runs about 30 miles to Tonbridge. It is therefore quite short for Train Simulator, but it has many stations. The developers have nevertheless added an 7 miles extension from Strood to Gravesend, next to the Thames River. All this combined with the CML, the add-on allows you to cover 82 miles, enough to have fun for a long time.
After the introduction, let's come to the game experience. The scenery is really pretty, we feel the atmosphere of the Kent countryside with the line that winds between the hills and the Medway River - which is often relatively close to the track for our pleasure. Stations and other landmarks are very well modelled, as usual for DTG. They don't forget the details, since some tags and rubbish can be found on the tracks. On the other hand, the distance scenery is sometimes (rarely) absent, but you won't notice anything if you are inside the cab. The ambient sounds are also there, although I would have preferred to hear more.
Let's move on to the rolling stock included: it's a small disappointment for me, because everything is already familiar. Concerning the EMUs, it is the same rolling stock that was available with the CML, namely Class 375 and 465 in different liveries. These two are also included in many English add-ons, so nothing new here. On the other hand, it is quality rolling stock, even if we can deplore a slight lack of functionalities. Regarding freight, the add-on includes Class 59, which was not in the CML, but was included in other British DLCs. So we can finally drive freight trains in Kent County!
Concerning the additional scenarios compared to the CML, 9 career missions are included with 4 Railfan scenarios and 2 Quick Drive. All of them have a large number of AI trains, so you will never feel alone on the line. And if we count the scenarios already provided with the CML, then the total number of career missions is 17 ; however, some scenarios go together.
I will finish with a quick overview of the CML. This line, published in 2016, is also a pleasant surprise for me, since I had never tested it before. The scenery is of the same level as in the Medway Valley, but the many stations in the London suburbs contrast with the bucolic countryside of Kent and give rise to more challenging scenarios. The only weakness of the CML is that some parts of the route duplicate the London-Brighton and the London-Faversham lines that I already own; however, these are relatively short sections.
To conclude, I would like to say that this network is one of DTG's best achievements in Great Britain, although I regret the lack of originality in the rolling stock. Its only drawback is its usual price, but since it is testable and buyable at -50% until Monday, I can only encourage you to try it!