"I have no ambitions to take another job".
I've always thought Everton was a great club.
The former Sunderland and Crystal Palace manager has a proven track record at avoiding relegation but is likely to need a few new signings in order to pull it off.
Everton are now sitting 17th in the table, two points ahead of the Hammers. But the chance to turn around Everton's faltering ship has lured him back, and Allardyce is expected to have a watching brief at Goodison Park on Wednesday night.
The sacking of Ronald Koeman in October has not produced the desired effect, with Everton recording one win, one draw and five defeats in all competitions since Unsworth took over.
The club's prospects had appeared so different at the beginning of the season with Everton having invested heavily following last season's impressive seventh-place finish.
The 63-year-old will manage his first match when Everton host Huddersfield Town on Saturday.
While Everton spent more than £130 million this past summer on signings such as Gylfi Sigurdsson, Jordan Pickford, Michael Keane and Davy Klaassen, in addition to adding Wayne Rooney on a free transfer, the Toffees have struggled to cope with the exit of leading scorer Romelu Lukaku to Manchester United.
He previously held talks with the club's hierarchy only to announce he had withdrawn because he felt they were hesitating.