UK electricity provider International Power has returned to London's blue-chip FTSE 100 index after a two-and-a-half-year absence.
International Power has interests in 15 countries
The FTSE Group confirmed on Wednesday that the company formed in October 2000 from the demerger of National Power would replace oil firm Cairn Energy.
Cairn joined the index last September after its value soared 400% on the back of a series of finds in India.
But its shares slumped two months later after a disappointing drilling update.
The firm recently said a Rajasthan oil field was larger than previously thought, but a subsequent recovery in its share price was not enough to retain its place in the FTSE 100.
Compiler FTSE reshuffles the benchmark index four times a year based on the market capitalisation of the constituents.
In addition to changes to the FTSE 100, the FTSE Group also said that MyTravel Group, British Energy Group and Savills would join the FTSE 250.
The three firms will replace Chrysalis Group, DX Services and Alba, who all fall from the FTSE 250 to the FTSE SmallCap index.
The changes will come into effect from the close of trade on Friday 18 March.