A timber bridge was probably built using army labour and engineering skills after the invasion of AD43, possibly in about AD52, on the line of Fish Street Hill to the southern abutment of today’s London Bridge. This would almost certainly have required restoration or repair after the Boudican revolt. Even if it had not actually been damaged or destroyed, the maintenance of the bridge must have suffered. It was much quicker, therefore, to use ferry boats to cross the river at that time.
That original invasion-period bridge was probably not intended to be permanent. Another temporary timber bridge was built in about AD85-90 from a site in Pudding Lane (PDN81) to a point on the south bank near the modern bridge abutment. It was built slightly off-line to allow for the existing temporary bridge to be replaced by a more permanent structure when the time came to replace it.
A new permanent bridge was built on the line of the original structure after about AD90 but before AD120, possibly with masonry piers and a timber decking capable of maintenance and replacement but excavations found little surviving evidence for it.
For further information, see Londinium's Bridge in Public life.