A leak feels urgent because it is happening inside the house. The safest response is to limit damage below, gather useful information and avoid turning a roof problem into a fall or electrical problem.
Protect the room first
Move furniture and valuables away from the wet area. Use a container for drips and protect flooring. If water is close to electrical fittings, do not touch wet electrics; isolate the affected circuit only if you can do so safely and seek appropriate electrical help.
Do not climb onto a wet roof
Rain, moss, steep pitches and loose tiles make roofs hazardous. Photos from ground level or a loft inspection from a safe boarded area are useful, but a leak is not worth a fall.
Note when the leak happens
Does it appear only in wind-driven rain? After prolonged rain? Around a chimney? Does it continue after the rain stops? Those observations help narrow the likely route of water.
Do not seal random areas with silicone
A quick smear can make later diagnosis harder and may trap water or fail because it is not compatible with the roofing material. Temporary weatherproofing should still be deliberate.
Related help
This guide is general information, not a substitute for inspecting the individual roof or checking current planning/building requirements for a specific property.