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                                                                   EXHIBIT 99(a)

                         [MID OCEAN LIMITED LETTERHEAD]

FOR IMMEDIATE RELEASE

CONTACT:            John M. Wadson             Andrew R. Baer/Tracey T. Stearns
                    Mid Ocean Limited          Kekst and Company
                    (441) 292-1358             (212) 593-2655



                MID OCEAN LIMITED ADOPTS SHAREHOLDER RIGHTS PLAN

                  Hamilton, Bermuda, September 12, 1996 -- Mid Ocean Limited
(NYSE: MOC) announced today that its Board of Directors adopted a Shareholder
Rights Plan designed to enhance the Board's ability to protect shareholders
against, among other things, unsolicited attempts to acquire control of Mid
Ocean that do not offer an adequate price to all shareholders or are otherwise
not in the best interests of Mid Ocean and its shareholders. The Plan has been
designed to exempt the existing holdings of EXEL Limited, a 29.8% shareholder of
Mid Ocean, as described below.
                  Under the Plan each holder of ordinary shares at the close of
business on October 1, 1996 will receive a distribution of one right for each
Class A Ordinary Share held. Each right entitles the holder to purchase from Mid
Ocean one Class A Ordinary Share at an initial purchase price of $140. The
rights will become exercisable and will detach from the Class A Ordinary Shares
a specified period of time after any person has become the beneficial owner of
20% or more of Mid Ocean's Common Shares or commenced a tender or exchange offer
which, if consummated, would result in any person becoming the beneficial owner
of 20% or more of the

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Common Shares. Persons (such as EXEL) owning 20% or more of the Common Shares of
Mid Ocean on the date the Plan was adopted, and certain transferees of such
persons, would not cause the rights to become exercisable, subject to certain
limitations on such persons' ability to acquire additional Common Shares.

                  If any person becomes the beneficial owner of 20% or more of
Mid Ocean's Common Shares (other than persons referred to in the previous
sentence), each right will entitle the holder, other than the acquiring person,
to purchase for the then applicable purchase price Mid Ocean Common Shares
having a value of twice the purchase price.

                  If, following an acquisition of 20% or more of Mid Ocean's
Common Shares, Mid Ocean is involved in certain mergers or other business
combinations or sells or transfers more than 50% of its assets or earning power,
each right will entitle the holder to purchase for the then applicable purchase
price common stock of the other party to such transaction having a value of
twice the purchase price.

                  At any time after a person has acquired 20% or more (but
before any person has acquired more than 50%) of the Company's Common Shares,
Mid Ocean may exchange all or part of the rights for shares of Common Shares at
an exchange ratio of one Class A Ordinary Share, less the par value of the Class
A Ordinary Shares, per right.

                  Mid Ocean may redeem the rights at a price of $.01 per right
at any time prior to a specified period of time after a person has become the
beneficial owner of 20% or more of its Common Shares. The rights will expire on
October 1, 2006, unless earlier exchanged or redeemed.

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                  Details of the Plan are outlined in materials that will be
mailed to all shareholders of Mid Ocean.

                  Michael Butt, President of Mid Ocean, said: "The rights are
intended to enable all Mid Ocean shareholders to realize the long-term value of
their investment in Mid Ocean. They will not prevent a takeover of Mid Ocean.
However, the rights plan should encourage anyone seeking to acquire Mid Ocean to
negotiate with the Board prior to attempting a takeover."

                  Mid Ocean Limited, through its wholly owned subsidiary, Mid
Ocean Reinsurance Company, Ltd., is a leading reinsurer, providing property
catastrophe, property risk excess of loss, property pro rata, marine, energy,
aviation, satellite, and other reinsurance to insurers on a worldwide basis. It
is majority shareholder in the Brockbank Group and has provided corporate
capital to Lloyd's syndicates managed by Brockbank's managing agency.

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