Mazda and Fiat have signed the final agreement that will see Mazda building a new rear-wheel drive Alfa Romeo roadster at its Hiroshima factory. Starting in 2015, Mazda will build the next generation of its own iconic MX-5 and use the same production line to produce the new two-seat convertible Alfa Romeo.

The two models will share a chassis, which can be no bad thing for Alfa given the MX-5’s reputation as a fine-handling sports car. Where the two will differ is in styling, set-up and engine – the Alfa version will use its own powerplant, with technical differences between the two not due to be confirmed for a long time.

Through the agreement, Mazda hopes to rekindle the waning interest in open-top driver’s cars and thus sell more MX-5s, while Alfa badly needs an accessible and technically impressive model to revive its fortunes and rebuild a once-key part of its heritage.

Combining the excellent MX-5 chassis and what is hoped will be a characterful, thrilling engine, the baby Alfa convertible will be one of the most eagerly anticipated cars of 2015.