There should be an oven burner trim, but it only stick up about an inch
Has it always done this?
Not to deflect but to protect - it sits in front of the flames.
If it is burning at the back then it could be a problem with the thermostat, please check that the flames return to low when fully heated and the temperature is reached.
It will have to come direct from Rangemaster spares department.
Check the picture to see if it is fitted