With a first-instance career lasting a few months short of twenty years, Alan Abraham Mocatta emerges roughly equal with Sidney Rowlatt as the longest-serving of all Commercial Judges. This is fitting, since Mocatta edited an edition of Rowlatt's text on guarantees, although he established his enduring professional reputation as an outstanding shipping lawyer.

Mocatta was born in 1907 into a prominent London Sephardic family. The Mocattas had a good claim to have been among the first Jews to settle in England after Cromwell permitted their return in the mid-17th Century, more than three hundred and fifty years after Edward I had expelled them from the realm in a tawdry attempt to bolster his flagging popularity ratings. Mocatta’s ancestors arrived in London from Holland, where they had made their way after being hounded out of their ancient home in Portugal during the late 15th Century expulsions. The Mocattas started out in London as diamond dealers, became bullion brokers with a dominant position in the gold and silver markets, and diversified into other professions, including the law, during the 20th Century.

Mocatta made an important contribution to this evolution, raising the set's profile with his hugely successful commercial practice. From his first reported case in The 'Portofino' (1933) 47 Lloyd's Rep 165 (a demurrage dispute, and an illustration of the sound principle, since abandoned, that a promise to perform an existing obligation did not constitute sufficient consideration to support a contract), his name featured regularly in the law reports, almost always in shipping cases. Henry Willink's appointment as King's Counsel in 1935 proved a happy event not only for Willink but also for Mocatta, who, to Judge from the number of cases in which they worked together, quickly became Willink's junior of choice. Mocatta also worked with other prominent commercial KC's, including Frederic Sellers, and, by the end of the 'thirties, was arguing cases on his own in the Commercial Court and  occasionally in the Court of Appeal. Given Mocatta's firm maritime focus, his editorship of the 3rd edition of 'Rowlatt On Principal & Surety' in 1936 was a rather mystifying departure from his usual field. Nonetheless, The Law Times welcomed Mocatta's "unusually good and highly useful" contribution to legal literature, although it noted that he was compelled to acknowledge that "the law on several aspects is not at the moment any too clear.”.

Back on more accustomed territory, Mocatta strengthened his reputation as a shipping specialist by joining McNair as editor of four editions of  'Scrutton On Charterparties' between 1939 and 1964. After McNair retired, Mocatta was senior editor for the 18th and 19th editions. He also contributed to the 1938 edition of 'Chitty On Contracts', but he did not become an established member of the senior editorial team. Nor did he produce any further editions of 'Rowlatt'

Just as Mocatta was establishing himself as one of the more prominent junior barristers in shipping litigation, his career was interrupted by the Second World War. Joining an anti-aircraft unit, he served with the guns until 1942. He then held a staff post at the War Office until 1945, left the army as a lieutenant-colonel, and was awarded the OBE for his wartime services.

3 Essex Court had completely closed down for the duration of the War. It re-opened in 1945 (McNair had paid the rent on the empty building for six years), but, as a result of deaths, retirement, or destruction of premises during the Blitz, several of its pre-War rivals never resumed business. This enabled the set to achieve a dominant position in commercial litigation over the next decade and a half. McNair had become the chambers' second KC in 1943 (while on secondment to the Ministry of War Transport), and the junior tenants included John Megaw and Eustace Roskill, both of whom - like Mocatta - would go on to become Commercial Judges. Mocatta quickly re-established his practice after he was demobilized from the army, with ten reported cases in the Lloyd's Law Reports for 1948, and greater numbers in subsequent years. Particularly prominent was Chandris v Isbrandtsen-Moller [1951] 1 KB 240, a key authority on a charterers' liability for shipping dangerous goods (at least at the trial before Patrick Devlin; by the time the case reached the Court of Appeal, it was all about awards of interest). As before the War, Mocatta’s core focus was on shipping work, primarily disputes under charterparties and bills of lading, and claims for loss or of damage to goods on board ship or during loading or discharge. He also appeared in marine insurance litigation and disputes about sale of goods carried by sea. But, one way or another, there was almost always a ship somewhere in any case in which he was involved. During this second phase of his career, Mocatta made the occasional venture into the Admiralty, although he never really developed a practice in collision, salvage, or towage and pilotage.

During the 1940's, Mocatta argued cases on his own more often than not, although he was led several times by McNair and by future Commercial Judge Patrick Devlin, and ocassionally still by Willink. But Willink, who had become an MP during the War and been Minister of Health in Churchill's wartime government, did not fully re-commit to practice at the Bar after 1945, and gave up altogether when he became Master of Madgalene College Cambridge, in 1948. Mocatta and the other 3 Essex Court juniors were able to pick up pieces of Willink's practice, and Mocatta was appointed King's Counsel in 1951. By then, his professional position was so secure that the change from junior counsel to leader was entirely natural, and did not affect the smooth flow of his career: he appeared in around a dozen reported cases in his first year as a KC.

By 1961, 3 Essex Court had lost not only Willink, but also McNair and Megaw, who had both gone on the Bench. But, with the acquisition of a collection of outsanding junior tenants, including Donaldson, Kerr, Anthony Lloyd, Michael Mustill, Christopher Staughton, and Anthony Evans, future Commercial Judges all, it had not just maintained but strengthened its position as the pre-eminent commercial chambers. So when the Lord Chancellor's Department announced that Queen's Counsel appointments would be regulated in future to ensure that no chambers had more than two QC's (ostensibly in the interests of maintaining a competitive market), there were suspicions that the innovation was directed specifically at 3 Essex. Whether or not that was right, the fact that Donaldson and Kerr had both been approved for appointment as QC's, but strictly subject to compliance with the new two-per-set rule, meant that the chambers had to break up. The plan was for Mocatta to remain as head of a diminished 3 Essex, with Roskill taking half of the tenants to found a new set next door at No 4. But, before this could be implemented, the Lord Chancellor dealt 3 Essex Court another blow. In October 1961, there was a re-shuffling of former and existing Commercial Judges. Patrick Devlin's brief tenure as a Lord Justice of Appeal was abruptly terminated when he replaced Frederick Tucker (who retired) in the House of Lords, and Kenneth Diplock took Devlin's place in the Court of Appeal. Mocatta was offered, and accepted, a place on the Queen's Bench neatly slotting into the Commercial Court vacancy created by Diplock's promotion. His elevation came nine months after John Megaw's and six months before that of Eustace Roskill's (who stayed - briefly - at 3 Essex after all), the middle link in a chain of events which must have appalled their senior clerk, who had been entitled to receive a percentage of their earnings at the Bar. The judicial appointment in rapid succession of three commercial practitioners from the same chambers was noted by the national press. In April 1963, The Observer gleefully informed its readers that "in the last 10 days, in almost unprecedented succession, Mocatta, Roskill, and Megaw have had decisions reversed by the appeal courts" (in slipping-and-tripping, landlord and tenant, and criminal cases respectively). The paper pompously suggested that the moral lesson was that "the rarefied atmosphere of the charter-party is not necessarily the best training for the robust world" of the Queen's Bench.

Aside from being a successful Judge, Mocatta was also a popular one, with a reputation for patience and for carefully listening to all sides of the argument. These were not attributes which were always associated with his near contemporary, John Megaw, who nevertheless went to the Court of Appeal after only eight years, and it seems surprising that Mocatta spent his whole career at first instance. Conceivably, he was seen as too much of a specialist for the wide range of work in the Court of Appeal. Mocatta regularly tried personal injuries cases and dealt with crime both on Circuit and in the Court of Appeal (Criminal Division), although he had no criminal experience at the Bar (In 1962, he presided over the mammoth fifty-five day trial at Camarthen Assizes of three men accused of making fraudulent agricultural subsidies claims. Mocatta's summing up to the jury lasted thirty four hours. The defendants were all convicted.) But the profile of his reported cases suggests that he had little interest in the defamation, landlord and tenant, local government, planning, real property, tax, and other general common law work which other Queen's Bench Judges accepted as part of the job. Moreover, he appears, like Clement Bailhache nearly half a century before, to have spent more and more time in the Commercial Court as his career went on. He was made President of the Restrictive Practices Court in 1970, but no other form of promotion came his way.