Source: ADM199/184 LL sweep in Fleet Minesweepers From DTM Admiralty Date: 12th July 1940 To: DEE  The subjoined extracts from a report on recent sweeping operations carried out by HM Ships HMS Bramble and SPEEDY are referred for information and comment. It is of interest to note that this is the first clearance operation by the LL sweep of a defined area known to contain magnetic mines. The sweep was for RED mines only and three were exploded. It is considered that the gear was subjected to a fair test since out of a total of 77 ¼ hours under way, 54 ¼ were spent actually sweeping.  Ships were stationed 220 yards apart in under 10 fathoms and 250 yards apart in 10 fathoms and over. The average speed of sweeping over the ground was 6 ¾ knots.  1st mine exploded almost underneath starboard sweep 70 yards astern of short tail. 2nd mine midway between sweeps, 70 yards astern of short tail. 3rd mine nearer port sweep 30 yards astern of short tail. No damage was done to the Callender Cable in either ship by the 3 detonations, even though one mine detonated almost directly beneath Bramble’s tail.   From:               The Senior Officer, 1st Minesweeping Flotilla, HMS Bramble Date:                17th June 1940 To:                   The Commander in Chief, Home Fleet.  Sweepers:         Bramble, SPEEDY Danlayers:        Yacht Seaflower, Drifters Guiding Light and Olive Tree.  Wind:               Light, variable, usually freshening force 2 from the ENE in the evenings. Visibility:          Considerable fog which stopped sweeping whenever visibility dropped below one mile.  Mines:              All ground magnetic. 1st Mine:           129° Tarbat Ness Lt House 4.45 miles, almost underneath starboard sweep, 70 yards astern of short tail. 2nd Mine:          136½° Tarbat Ness Lt House 3.45 miles midway between sweeps, 70 yards astern of short tail. 3rd Mine:           141½° Tarbat ness Lt House 3.5 miles nearer port sweep, 30 yards astern of short tail.  No damage was done to the Callender Cable in either ship by the 3 detonations, even though one mine detonated almost directly beneath Bramble’s tail.  Although the two drifters acting as danlayers had never before carried out this duty, they worked extremely well and efficiently. They had only two cork dan buoys when they arrived, but six complete dans were lent from the sweepers. It is urgently requested that these two drifters may be allocated to the 1st MSF for danlaying duties. They are eminently more suitable than the yachts Hinba and Bunting who have recently been taken away for there duties. If danlayers are not provided permanently and thus gain experience, it cannot be expected that clearances can be accurate under conditions when navigational fixes are not continuously available. The yacht Seaflower proved herself a most efficient and suitable danlayer.    Diary of Events during Magnetic Clearance of QZX44    Harbour LL       Date Left Returned Out In Hours swept Laps swept Remarks Tues 4th June 1135 1920 1250 1730 4.7 4 Meeting of CO’s of sweepers and danlayers prior to sailing Weds 5th June 0730 1835 0830 1655 8.5 6   Thurs 6th June 0730 - 0840 1200 3.3 3 Owing to fog, ships had to anchor from 1200/6 to 1100/7 Fri 7th June 1100 1645 1116 1454 3.5 3 Fog Sat 8th June 0940 2140 1050 2000 9.0 6 Drifters coaled 0630 to 0815 Sun 9th June 1000 - 1110 1725 6.2 3 Fog, anchored at 1020 Mon 10th June 0720 1830 0805 1645 7.0 6 Fog, anchored between 1100 and 1240 Tues 11th June 0700 2130 0830 2030 12.0     Total hours sweepers under way            77 ¼ Total hours sweepers sweeping              54 ¼ Total hours danlayers under way           90 ¼ Average speed of sweeping                     6 ¾ knots