What rateing is your RCD?
Just as a guide:- 2.5 mm-20 amps Up to 4800 Watts so your cable provided its 2.5 is fine.
Electrical cables are intended to become warm in operation; heat is generated whenever a current flows in anything, and this is perfectly normal. However, the level of heat generated by electrical cables is only safe when it is kept within reasonable limits. Standard PVC-insulated cables are designed to run at temperatures up to 70 degrees Celsius; beyond this there is a risk of damage.
In practice, over-currents can be grouped into two types.
Overload
An overload occurs when a current flows that is somewhat too high (usually 50% to 100% too high) for the system. Overloads don't normally cause immediate, catastrophic damage. Instead, the likelihood of damage increases gradually as the duration of the overload increases. If the fault is not resolved, cables will overheat and melt, exposing bare conductors. The heat generated may be sufficient to cause a fire.
In a domestic setting, overloads usually result from using too many appliances at the same time, or plugging a heavy-duty appliance into a supply that isn't strong enough for it. An example of the latter is connecting an electric shower to a standard 13-amp plug, and plugging it into a socket