New Lease

19 June 2006

    Slough Estates in major 325,000 sq ft biotech letting in North America     

         Also announces additional 43,000 sq ft lease with new client          

Slough Estates International ("SEI") has signed a major new leasing and
development arrangement with one of the world's largest biotechnology companies
with a market capitalisation of over $80bn. This deal reinforces SEI's position
as a pre-eminent developer and owner of biotechnology facilities in the San
Francisco Bay area.

The existing tenant requires a significant expansion of its current space to
accommodate recent acquisitions and future expansion plans in the Bay area. The
tenant has committed to three buildings totalling approximately 325,000 square
feet at SEI's biotechnology campus in the City of South San Francisco with an
option on a fourth building with a further 85,000 square feet. Following the
completion of these new commitments and of one other building already under
construction this one tenant will be leasing approximately 755,000 square feet
from SEI.

Although the financial terms of the agreement remain confidential, the initial
yield achieves SEI's target levels for this prime market, and the contracted
future rental performance is attractive.

SEI expects to invest about $170 million in the development of the project.
Construction will commence immediately and will comprise tenant improvements
for an existing vacant 81,000 square foot facility at Britannia Oyster Point I
and construction of the first two new buildings at Britannia Oyster Point II.
Delivery is expected in 2008.

This major new leasing agreement further demonstrates the attractiveness of
South San Francisco as a location of choice for the biotech industry, in
particular maintaining the growth momentum of the Bay Area biotech cluster. It
reinforces the quality of SEI's development franchise in these biotech markets,
with two of the largest biotech companies in the world having firmly
consolidated their presence in the South San Francisco market.

Following the completion of this campus and other contracted development in the
pipeline, SEI's biotech presence in the both San Diego and in the San Francisco
Bay Area will grow from 4.3 million square feet to about 5.4 million square
feet, including 4.7 million square feet in the San Francisco Bay Area and 2.8
million square feet specifically in South San Francisco.

Ian Coull, Chief Executive of Slough Estates plc said:

"In successfully agreeing new terms with one of the world's largest
biotechnology companies, we continue to demonstrate how our US division is
taking a lead in the biotech sector. I am particularly pleased as this is an
existing client: this kind of long term close client relationship is typical of
Slough Estates USA's brand profile and has been a key contributor to the
expansion of the business franchise. This agreement demonstrates how we
continue to maximise the value of the US business. Our confidence in the San
Francisco Bay area and in biotechnology as a sector of focus has been fully
justified."

43,000 lease with OncoMed Pharmaceuticals Inc

In addition to this agreement, SEI has also signed a new agreement with a fast
growing, early-stage biotech company, which develops novel therapeutics that
target cancer cells. The 7-year lease starts April 2007 on a 43,000 square foot
facility on the Britannia Seaport Centre site.

                                    -ends-                                     

For further information please contact:

Slough Estates plc                              Maitland                       
                                                                               
Michael Waring                                  Colin Browne                   
                                                                               
Tel: [phone]                               Tel: [phone]             

Slough Estates International

Slough Estates is the leading European provider of flexible business space and
owns business parks in Europe and North America, with four million square
metres of business space and over 1600 customers (as at 31 December 2005).
Slough Estates' properties are in suburban locations in close proximity to the
main business centres, where there is long term demand for business
accommodation to serve these key economic regions. The company's main
activities are currently based around London, Brussels, Paris, Düsseldorf,
Amsterdam, San Francisco and San Diego and the company continues to develop new
business parks with the long term objective of building shareholder value and
enhancing its reputation for quality buildings offering excellent value to
customers. www.sloughestates.com