Mallinckrodt has taken the entire second floor of the building at a yearly rent of £703,352 (£34.50 per sq ft).
3 Lotus Park is within walking distance from Staines town centre, providing 68,448 sq ft of Grade A office space.
Staines is seen as being one of the key office centres in the western corridor and is within easy reach of Heathrow, the M25 and Central London.
Hanover Green acted for Legal & General on this transaction.
Kevin Hawthorn of Hanover Green said: “The rent per sq ft achieved on this letting is the highest in Staines and is indicative of the upward rental trend for Grade A office space in the Thames Valley.
“We are confident of securing at least a similar rental level for the remaining 46,500 sq ft at 3 Lotus Park.”