Bike porn

Bit confused by this. 360 drops, low standover and maguras made me think street/trials bike but Thomson layback, chainring/guard and bolt on fixed gear suggest not. Also don't understand the roller/chain tensioner thing. Surely it can't be spring loaded if it's being run fixed? Maybe adjustable somehow?

I was going to say it was for chain retention rather than tension but given the lack of track ends you're either looking at an eccentric rear hub or magic gear to ensure tension, so it looks like they have bodged that as a combination chain retainer and tensioner? Given where it sits on the chain and the fact it pushes up rather than forces down might enable the bike to be fixed without bending the tensioner

Just to add: because it looks like a flipped rear wheel with cassette removed and sprocket bolted onto the disc brake bracket