Press Release

MARCONI ANNOUNCES THE BXR-5000 EDGE ROUTER

First Product from New Marconi - Laurel Networks Partnership

Pittsburgh, PA - May 28, 2003 — Marconi Corporation plc (London: MONI) today announced the availability of the BXR™-5000 edge router as part of a partnership between its Broadband Routing and Switching group and privately held Laurel Networks, Inc. The BXR-5000 will complement Marconi's existing solutions for U.S. Federal government network operators and global service providers.

Under the partnership, Marconi introduces the BXR-5000, a scalable 160 Gigabits per second per rack platform (80 Gbps in and 80 Gbps out) that supports the aggregation of high-density Gigabit Ethernet (GigE) into a high-speed multiservice core over OC-48c / STM-16 (2.5 Gigabits per second) or OC-192c / STM-64 (10 Gigabits per second) circuits. Complementing Marconi's BXR-48000, a 960 Gbps (480 Gbps in and 480 Gbps out) switch-router, the BXR-5000 supports the high-density, high-speed aggregation using Packet over Sonet / Synchronous Digital Hierarchy (POS / SDH) or Asynchronous Transfer Mode (ATM) transport protocols, delivering high-bandwidth, next-generation performance today with commercially-available, standards-based Quality of Service (QoS) and encryption support required by mission-critical network operators.

"Through this partnership, Marconi combines its strong relationships in the federal market and best-in-class multiservice switching technology with Laurel's world-class IP routing," said Mark Bieberich, Senior Analyst Communications Network Infrastructure, of Yankee Group. "As the operators of government networks expand their switched and routed networks, this provides a compelling solution for delivering new IP and MPLS services
while also maintaining support for legacy services."

The agreement, which includes sales, marketing and development activities, provides a complementary solution to Marconi's BXR, ASX™ and TNX™ products. In addition to providing aggregation of high-density GigE and Internet Protocol (IP) services, the BXR-5000 addresses the requirements of U.S. Federal government markets for IP Quality of Service along with the benefits of plug and play provisioning of network elements with self-configuration, self-healing and simple management of large, flat networks. This agreement complements the recently announced partnership with Riverstone Networks, which enables Marconi to combine its Softswitch with a GigE router to provide a competitive voice over IP (VoIP) networking solution.

"Marconi has established a leadership position with their world-class switching technology in the federal market and among many key carriers," said Steve Vogelsang, co-founder and vice president of marketing, Laurel Networks. "Introducing Laurel's innovative IP edge routing technology into the Marconi portfolio enables a best-of-breed solution that combines the best of both switching and routing."

The partnership also provides the robust network characteristics such as scalability, predictability, reliability, security and flexibility required for real-time applications that include transport of multimedia, high-performance computing and high-resolution imagery.

"With this agreement, Laurel and Marconi have forged a partnership to deliver unique benefits to Marconi customers," said Tom Murray, vice president of marketing, Marconi's Broadband Routing and Switching group. "We are committed to delivering a robust solution that ensures the best performance for current and emerging broadband services."

About Marconi Corporation plc
Marconi Corporation plc is a global telecommunications equipment, services and solutions company. The company's core business is the provision of innovative and reliable optical networks, broadband routing and switching and broadband access technologies and services. The company's customer base includes many of the world's largest telecommunications operators.

The company is listed on the London Stock Exchange under the symbol MONI. Additional information about Marconi Corporation can be found at www.marconi.com.

About Laurel Networks
Laurel Networks is leading the creation of The New Service Delivery Architecture to enable profitable delivery of data and IP services at the edge of carrier IP/MPLS networks. Laurel's service edge routers and service management software are evolving carrier architectures from multiple data networks to a single packet-switched architecture with minimal capital investment. Combining carrier-class routing, data switching, advanced QoS and high availability, Laurel service edge routers support both routed and switched services. This unmatched service agility allows carriers to evolve their service portfolio to meet changing market requirements. Laurel Networks was founded in 1999 and is headquartered in Pittsburgh, Pennsylvania. For more information, visit www.laurelnetworks.com.

Notes to Editors
Marconi's Broadband Routing and Switching group and Laurel Networks share a common heritage of developing and building networking equipment using software and hardware architectures that adhere to the most rigorous specifications for performance and reliability. Both are based in Pittsburgh, where they are combining their networking expertise to solve a variety of complex communications problems for the U.S. Federal government and other network operators.

Press enquiries:

Marconi: Geof Becker
tel: 724-742-6377
email: geof.becker@marconi.com

Laurel Networks: Kimberly Booth
tel: 412-809-4298
email: kbooth@laurelnetwoks.com

This press release contains forward-looking statements with respect to products, partners, customers, future growth and other matters. Please refer to the Form 20-F report and Form 6-K reports filed by Marconi Corporation plc with the United States Securities and Exchange Commission for a discussion of risks that could cause actual results to differ materially from such statements.