When Lucan left the Light Brigade idling on the plateau, he instructed Cardigan to defend the position against attack.
Cardigan interpreted this to mean that he should not leave the plateau, and the Brigade remained mostly immobile while the Heavy Brigade engaged the Russian cavalry (over the objection of some of the Light Brigade's officers).
This prevented the British cavalry from adequately pursuing the Russians, and no attacks were mounted down the North Valley through which they had retreated.
Due to the failure of their attack, the Russians chose not to advance further, leading to Raglan deciding to attempt to retake the captured Turkish fortifications using the Light and Heavy brigades with two divisions of infantry.
Although the 1st Division advanced swiftly, the 4th Division was deliberately slow, making Raglan increasingly impatient.
He dispatched an aide to Lucan ordering that "Cavalry to advance and take advantage of any opportunity to recover the heights.
They will be supported by the infantry which have been ordered to advance on two fronts".
 Lucan interpreted this to mean he should await the infantry support before attacking.

About 40 minutes later, with the infantry still having not arrived, Raglan's staff officers spotted Russian artillery teams approaching the fortifications with equipment to remove captured guns.
To avoid the guns being taken, Raglan dispatched Nolan to carry a message to Lucan that read:
Lord Raglan wishes the cavalry to advance rapidly to the front, and try to prevent the enemy carrying away the guns.
Troop of horse-artillery may accompany.
French cavalry is on your left.
Immediate.

As Nolan rode towards Lucan's position, Raglan shouted that he should "Tell Lord Lucan the cavalry is to attack immediately"; his fourth order.
The Russian forces included the Don Cossack field artillery battery, containing between eight and twelve guns, drawn up at the bottom of the North Valley, with regiments of cavalry waiting behind it.
Nolan carried the message to Lucan; when Lucan asked what guns were referred to, Nolan is said to have indicated, by a wide sweep of his arm, not the Causeway redoubts but the Don Cossack battery in the North Valley, around a mile away.
After a brief debate, Lucan ordered the Light Brigade forward.
Cardigan claimed that Lucan had ordered him to attack without quarter given, despite him pointing out the Russian artillery; Lucan, on the other hand, claimed he told Cardigan to retire from battle "if no opportunity to take his objective presented itself".

Regardless, the Brigade drew swords and was ordered by Cardigan to advance down the valley.
Nolan had explicitly asked to join the Brigade for the fight, and was allowed to.
When Lucan left the Light Brigade idling on the plateau, he instructed Cardigan to defend the position against attack. Cardigan interpreted this to mean that he should not leave the plateau, and the Brigade remained mostly immobile while the Heavy Brigade engaged the Russian cavalry (over the objection of some of the Light Brigade's officers). This prevented the British cavalry from adequately pursuing the Russians, and no attacks were mounted down the North Valley through which they had retreated. Due to the failure of their attack, the Russians chose not to advance further, leading to Raglan deciding to attempt to retake the captured Turkish fortifications using the Light and Heavy brigades with two divisions of infantry. Although the 1st Division advanced swiftly, the 4th Division was deliberately slow, making Raglan increasingly impatient. He dispatched an aide to Lucan ordering that "Cavalry to advance and take advantage of any opportunity to recover the heights. They will be supported by the infantry which have been ordered to advance on two fronts".  Lucan interpreted this to mean he should await the infantry support before attacking.
About 40 minutes later, with the infantry still having not arrived, Raglan's staff officers spotted Russian artillery teams approaching the fortifications with equipment to remove captured guns. To avoid the guns being taken, Raglan dispatched Nolan to carry a message to Lucan that read:
Lord Raglan wishes the cavalry to advance rapidly to the front, and try to prevent the enemy carrying away the guns. Troop of horse-artillery may accompany. French cavalry is on your left. Immediate.
As Nolan rode towards Lucan's position, Raglan shouted that he should "Tell Lord Lucan the cavalry is to attack immediately"; his fourth order. The Russian forces included the Don Cossack field artillery battery, containing between eight and twelve guns, drawn up at the bottom of the North Valley, with regiments of cavalry waiting behind it. Nolan carried the message to Lucan; when Lucan asked what guns were referred to, Nolan is said to have indicated, by a wide sweep of his arm, not the Causeway redoubts but the Don Cossack battery in the North Valley, around a mile away. After a brief debate, Lucan ordered the Light Brigade forward. Cardigan claimed that Lucan had ordered him to attack without quarter given, despite him pointing out the Russian artillery; Lucan, on the other hand, claimed he told Cardigan to retire from battle "if no opportunity to take his objective presented itself". 
Regardless, the Brigade drew swords and was ordered by Cardigan to advance down the valley. Nolan had explicitly asked to join the Brigade for the fight, and was allowed to.
Louis Nolan