*

UK reaches final investment decision

*

Canadian pension fund La Caisse takes 20% stake

*

UK to hold 44.9% in project

(Adds background throughout)

By Sarah Young

LONDON, July 22 (Reuters) - Britain gave the final

go-ahead for the 38 billion pound ($51 billion) Sizewell C

nuclear plant in eastern England on Tuesday after it secured

investment from British and international investors including

Canadian pension fund La Caisse.

Under the deal the British state will be the largest

shareholder in the project with a 44.9% stake, La Caisse will

hold 20%, UK energy firm Centrica ( CPYYF ) 15% and London-headquartered

Amber Infrastructure taking an initial 7.6%, joining France's

state-owned EDF which had already announced its 12.5% stake.

Britain needs to build new nuclear plants to replace its

ageing fleet, boost energy security, reach its climate targets

and create new jobs.

"Delivering next generation, publicly-owned clean power

is vital to our energy security and growth," finance minister

Rachel Reeves said in a statement.

The announcement of La Caisse as the second biggest

shareholder comes as a surprise after months of speculation that

Canadian investor

Brookfield

was in pole position to invest.

Sizewell will be only the second new nuclear plant built

in Britain in more than two decades, after French state-owned

EDF's Hinkley Point C. That has been beset by delays and cost

overruns, and is not due to start operating until about 2030.

First proposed in the early 2010s, Sizewell C was

originally going to be developed by EDF with China General

Nuclear Power Group, but the UK government bought out the

Chinese firm's stake in 2022 amid security concerns.

France's EDF has said it is investing around 1.1 billion

pounds in Sizewell, while Centrica ( CPYYF ) said in its statement it had

committed to construction funding of 1.3 billion pounds.

The government statement said Britain's National Wealth

Fund would provide the majority of the debt finance for the

project, alongside a debt guarantee from France's export credit

agency, Bpifrance Assurance Export.

($1 = 0.7424 pounds)