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The 1968 wiring rules still don't specify earthing lighting circuits unless there's a metal fitting on the circuit.

In the U.K. it was the 1966 IEE Regs. which introduced the requirement:

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D.6 At every lighting point an earthing terminal shall be provided and connected to the earth-continuity conductor of the final sub-circuit.

D.7 An earthing terminal, connected to the earth-continuity conductor of the final sub-circuit, shall be provided at every lighting switch position, unless this takes the form of an earthed metal box having a means of fixing the switch plate in reliable electrical contact with the box.

NOTE:- Regulations D.6 and D.7 are applicable even where a point or switch position is intended, at the time of installation, for the attachment of an all-insulated accessory or fitting or a double-insulated fitting. They are intended to allow for any later substitution of an accessory or fitting which needs to be earthed.

Prior to 1966, an earth was only required in certain circumstances.

The applicable exemption for lights is:

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403 ...Metal which is so isolated that it is not liable to come into contact with live parts or with earthed metal....need not be earthed. This exemption shall be restricted as detailed in the following clauses (i)-(ix)

{.....}

(ix) Lighting fittings using filament lamps installed in a room having a non-conducting floor, mounted at such a height that they cannot readily be touched and are out of reach of earthed metal.

(Quoted because Mike likes to read old regulations! [Linked Image] )