Looks to me like the lashings for securing the spare wheel on a LR Series 3 bonnet. If so, they should form a 'Y', with a hook on the end of the long leg which fits over a flattened hoop towards the front of the bonnet, while the ends of the shorter legs are secured by similar loops at the windscreen end of the bonnet. The mechanism is an 'over-centre' tensioner, with which to take up the slack.
In practice, we would stuff hessian, exhaust extensions, and other sundry stuff under the strap as well, although leaving the security of a rather hefty wheel/tyre combo to a UV light-degraded bit of plastic was probably a little optimistic.