Army, and a battery of 51sth (L) Hvy Rgt was among the artillery reinforcements thrown into this gap along the River Dendre, where there was fierce fighting. After leaving rearguards on the Dendre, the BEF occupied the Escaut line on 21 May, but by now the enemy was in its rear. To hold the line of the Aire Canal north of Saint-Omer the BEF organised a scratch force of rear elements ('Polforce'), including 51st (L) Hvy Rgt, to defend the crossings. The bridge at Saint-Momelin was held for three days against 1st Panzer Division by one gun of 98th (Surrey & Sussex Yeomanry) Field Rgt and the gunners of 51st (L) Hvy Rgt acting as infantry, equipped with nothing more than rifles and a few Bren guns. They had the satisfaction of intercepting a German radio message that said 'Bridge at Momelin strongly held, try elsewhere'. The defenders at St Momelin were relieved by French troops on 25 May and fell back into the 'pocket' round Dunkirk from which the BEF was preparing evacuation (Operation Dynamo). Home defence All the BEF's heavy equipment such as artillery had to be disabled and left behind in France, and this could only be slowly replaced. By the Autumn of 1940, 51st (L) Hvy Rgt with its attached Royal Corps of Signals section had joined Western Command, facing the possibility of German invasion by sea and air. The available heavy guns were sited within range of likely landing places. The regiment moved to Eastern Command in March 1941 and gained a Light Aid Detachment (LAD) of the Royal Electrical and Mechanical Engineers. On 11 March 1942 the regiment's four batteries were redesignated P, Q, R and S, and on 1 January 1943 they were numbered as 1, 2, 4 and 6 Heavy Btys. The anticipated invasion never came, and the field force in the UK began to prepare for offensive action once more. One innovation was the Army Group Royal Artillery (AGRA), a powerful artillery brigade, usually comprising one heavy, three medium and one field regiment, which could be rapidly moved about the battlefield, and had the punch to destroy enemy artillery. 51st (L) Hvy Rgt, together with its attached signal section and LAD, was assigned to 4 AGRA, formed in May 1943 as part of Second Army. By now, the RA's heavy regiments were equipped with two batteries of 7.2-inch howitzers and two