In one of the most surprising transfer deals ever sealed in English football, West Ham have signed coveted Argentina stars Carlos Tevez and Javier Mascherano - beating off competition from Manchester United, Arsenal, Bayern Munich and AC Milan. And Portsmouth.

The pair had been expected to join the Hammers from Brazilian club Corinthians on year-long loans, but a statement on the West Ham website this afternoon has revealed the moves are permanent, adding that the fee and "all other aspects of the transfers will remain confidential and undisclosed." Bearing in mind football market conditions, observers have generally considered each of the players to be worth in excess of £15m and there have been suggestions that West Ham have bought the players with a view to selling them on at the end of the season.

However, Hammers media spokesman Phil Hall was anxious to quash such speculation. "There is no way West Ham would act as a feeder club for others," he said of the club that has sold Frank Lampard, Joe Cole and Glen Johnson to Chelsea. "These are exciting signings for us but, of course, if we were offered major fees for the players at a later date we would have to consider it - as we would with other players."

News of the deal had first been broken on Tevez's official website this morning. "Carlitos Tevez - along with his former Corinthians team-mate, Javier Mascherano, has signed - a contract to play with West Ham United of England," read a statement.

The move is nothing short of sensational: never before have two world-class players yet to reach their prime - both are only 22 - rejected a host of elite clubs in order to join a middling one.

It is unquestionably a major coup for Pardew and gives last season's FA Cup runners-up one of the most impressive-looking squads in the Premiership.

It is not known what role, if any, was played in the transfers by Media Sports Investment (MSI), the company that two years ago agreed a 10-year partnership with Corinthians that effectively gave it control of the club. In 2004 the company was instrumental in bringing Tevez to the Brazilian club from Boca Juniors in an £11.4m transfer that amazed observers of South American football. MSI is run by Kia Joorabchian, the London-based businessman who last year expressed an interest in taking over West Ham. Spanish newspaper AS has reported that Roman Abramovich also has a 15% stake in the company, but Joorabchain has consistently denied that the Chelsea owner any link to MSI.

He has also rubbished claims that another Russian billionaire, Boris Berezovsky, owns part of MSI.

Regardless of how the deals were done, the players will unquestionably have a significant impact on West Ham's immediate future.

With the addition of Tevez, a prolific striker who's capable of being both subtle and barnstorming, Upton Park is now home to one of the most fearsome strikeforces in England. The Argentinian will surely be an automatic first choice, leaving Pardew the luxury of choosing between between Dean Ashton - when he returns to fitness - Bobby Zamora, Marlon Harewood, Carlton Cole and Teddy Sheringham.

Their midfield will also be formidable, with Mascherano, who Sir Alex Ferguson reportedly rated as the world's most worthy recipient of the "new Roy Keane" tag, likely to slot in alongside Reo-Coker, Benayoun and Matthew Etherington.

All of a sudden West Ham look an excellent bet to win this season's Uefa Cup - and have been transformed into genuine contenders for a Champions League spot.