The deal ends a troubled six months for the player, signed as a wing from the union club, Waterloo, but successfully converted to the front row by Doug Laughton, the then Widnes and now Leeds coach.
Howard played for Eastern Suburbs in Sydney during the summer and only returned reluctantly to training and playing for Widnes last month. He had threatened to sit out the remainder of his Widnes contract in Australia and join Easts permanently in May.
That possibility made a hefty fee from an English club a more attractive option. 'It has been a long drawn-out saga,' the Leeds chief executive, Alf Davies, said. 'Forwards of his ability are thin on the ground and he makes the Leeds pack look not bad at all.'
One of Howard's priorities will be to make up for lost time. His dispute with Widnes cost him the chance of a first Great Britain cap against New Zealand in October, but his prospects for this autumn must be bright now that Wigan's Andy Platt has committed himself to the Auckland Warriors.
Laughton has now been allowed to buy an entire new pack, large fees this season bringing in Neil Harmon, Richie Eyres and Howard to complement other expensive signings like Gary Mercer and Ellery Hanley.
Laughton has also invested heavily in backs such as Alan Tait, Craig Innes and Kevin Iro. Although Leeds' current run of three wins is their best of the season, a satisfactory return for such an outlay is still some way off.
The Widnes chairman, Jim Mills, views the transfer - like that two years ago of Martin Offiah, whose situation at Wigan Leeds are watching closely - as a case of bowing to the inevitable.
'We were reluctant to let him go but we realised that he wouldn't be playing for us after this season,' Mills said. We are now looking for a forward replacement, provided the right player is available.'
That will be an even more vital consideration with the news that Rod Howe, their Australian prop, has a back injury and may need to return home for an operation.
Tea Ropati, last season's First Division player of the year, is to leave St Helens for the Auckland Warriors at the end of this season.Reuse content