Good morning my name is ***** ***** I will assist you today.
The clicking noise you hear is the relay inside the TV which is trying to turn on the power to the electrical components inside the TV, this proves power is getting to the TV.
The most likely fault is the internal control board has failed and needs replacing, due to the age of the TV this is often uneconomical to repair, unless you can source second hand parts from ebay etc.
In order to prove this is an internal fault, please disconnect all the leads going to the TV (power supply, HDMI, Coax, Satelite, Scart, phono, fibre optics etc) and hold down the power button for 30 seconds (with everything unplugged), leave the TV for a further 5 minutes so we can be sure it is fully discharged, then plug only the power supply in, and try and turn the TV back on. If the same fault is present, this will require an engineer visit to replace the control board which can be upwards of £100.
Should you need any further assistance please let me know